Jozef Goetz contribution, 2011 1 Credits: Parts of the slides are based on slides created by textbook authors, P.J. Deitel and H. M. Deitel by Prentice

Jozef Goetz contribution, 2011

1

Credits: Parts of the slides are based on slides created by textbook authors, P.J. Deitel and H. M. Deitel by Prentice Hall


2

Conversion for me was not a Damascus Road experience. I slowly moved into a intellectual acceptance of what my intuition had always known. Madeleine L’Engle

Be careful when reading health books;you may die of a misprint. Mark Twain


3

Reckoners without their host must reckon twice. John Heywood

There was a door to which I found no key; There was the veil through which I might not see. Omar Khayyam


4OBJECTIVES

In this chapter you will learn: To manipulate data of various types. To use operators, arrays and control statements. To use regular expressions to search for patterns. To construct programs that process form data. To store data on the client using cookies. To create programs that interact with MySQL databases.


5

23.1 Introduction 23.2 PHP Basics 23.3 String Processing and Regular Expressions 23.3.1 Comparing Strings 23.3.2 Regular Expressions 23.4 Form Processing and Business Logic 23.5 Connecting to a Database 23.6 Using Cookies 23.7 Dynamic Content 23.8 Operator Precedence Chart 23.9 Wrap-Up 23.10 Web Resources


623.1 Introduction

PHP, or PHP: Hypertext Preprocessor, has become one of the most popular server-side scripting languages for creating dynamic web pages.

PHP is open source and platform independent—implementations exist for all major

UNIX,

Linux,

Mac and

Windows operating systems.

PHP also supports a large number of databases.


PHP was rated the best scripting language

The survey asked more than 500 developers to rate the scripting languages they use according to features and capabilities such as (http://www.infoq.com/news/2009/03/top-scripting-languages-php-ruby) : ease of use, exception handling, extensibility, maintainability/readability, cross-platform portability, community, availability of tools, quality of tools, performance, memory management, client-side scripting, and security.

Languages in the survey included: Actionscript, Flex, Java Script, F#, Windows Powershell, Perl, PHP, Python, Ruby, and VB Script

The study concluded that PHP was the best all-around scripting language for web applications with a large community and lots of readily available tools.

7


PHP most popular scripting language From PHP for theWeb ed 4 by Larry Ullman (2011) p Xiii:

PHP is most popular tool available for developing dynamic Web sites

PHP is in use on over 75% of all Web sites (Jan 2011) and it is the fourth most popular programming language overall

PHP can do certain task faster and more easily than the alternatives

open source nature means that PHP’s users are driving its development , not some corporate entity

PHP is used by: the biggest web sites Yahoo!, Wikipedia, Facebook, content management tools: WordPress, Drupal, Moodle, and Joomla

By learning you’ll provide yourself with either a usable hobby or a lucrative skill

8


923.2 PHP Basics The power of the web resides not only in serving content to users, but also

in responding to requests from users and generating web pages with dynamic content.

PHP code is embedded directly into XHTML documents, though these script segments are interpreted by a server before being delivered to the client.

PHP script file names end with .php.

Although PHP can be used from the command line, a web server is necessary to take full advantage of the scripting language.

In PHP, code is inserted between the scripting delimiters <?php and ?>.

PHP code can be placed anywhere in XHTML markup, as long as the code is enclosed in these delimiters.


1023.2 PHP Basics (Cont.) Variables are preceded by a $ and are created the first time they are

encountered.

PHP statements terminate with a semicolon (;).

Single-line comments which begin with two forward slashes (//) or a pound sign (#). Text to the right of the delimiter is ignored by the interpreter. Multiline

comments begin with delimiter /* and end with delimiter */.

When a variable is encountered inside a double-quoted ("") string, PHP interpolates the variable. In other words, PHP inserts the variable’s value where the variable name appears

in the string. All operations requiring PHP interpolation execute on the server before the

XHTML document is sent to the client.

PHP variables are loosely typed - they can contain different types of data at different times.


11 1 <?php print( '<?xml version = "1.0" encoding = "utf-8"?>' ) ?>

2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"

3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

4

5 

6 

7 <html xmlns = "http://www.w3.org/1999/xhtml">

8 <?php

9 $name = "Harvey"; // declaration and initialization

10 ?>

11 <head>

12 <title>Using PHP document</title>

13 </head>

14 <body style = "font-size: 2em">

15 <p>

16 <strong>

17 

18 Welcome to PHP, <?php print( "$name" ); ?>!

19 </strong>

20 </p>

21 </body>

22 </html>

Outline

first.php Delimiters enclosing PHP script

Declares and initializes a PHP variable

Interpolates the variable so that its value will be output to the XHTML document


12Common Programming Error 23.1

Failing to precede a variable namewith a $ is a syntax error.



Variable names in PHP are case sensitive.

Failure to use the proper mixture of cases to refer to a variable will result in a logic error, since the script will create a new variable for any name it doesn’t recognize as a previously used variable.



Forgetting to terminate a statementwith a semicolon (;) is a syntax error.


15

Type Description

int, integer Whole numbers (i.e., numbers without a decimal point).

float, double, real Real numbers (i.e., numbers containing a decimal point).

string Text enclosed in either single ('') or double ("") quotes. [Note: Using double quotes allows PHP to recognize more escape sequences.]

bool, boolean True or false.

array Group of elements.

object Group of associated data and methods.

resource An external source—usually information from a database.

NULL No value.

Fig. 23.2 | PHP types.


1623.2 PHP Basics (Cont.) Type conversions can be performed using function settype. This function takes two

arguments—a variable whose type is to be changed and the variable’s new type.

Variables are automatically converted to the type of the value they are assigned.

Function gettype returns the current type of its argument.

Calling function settype can result in loss of data. For example, doubles are truncated when they are converted to integers.

When converting from a string to a number, PHP uses the value of the number that appears at the beginning of the string. If no number appears at the beginning, the string evaluates to 0.

Another option for conversion between types is casting (or type casting). Casting does not change a variable’s content -it creates a temporary copy of a variable’s value in memory.

The concatenation operator (.) combines multiple strings.

A print statement split over multiple lines prints all the data that is enclosed in its parentheses.





4

5 

6 


8 <head>

9 <title>Data type conversion</title>

10 </head>

11 <body>

12 <?php

13 // declare a string, double and integer

14 $testString = "3.5 seconds";

15 $testDouble = 79.2;

16 $testInteger = 12;


18

19 

20 <?php

21 print( "$testString is a(n) " . gettype( $testString )

22 . "<br />" );

Outline

data.php

(1 of 3)

Automatically declares a string

Automatically declares a double

Automatically declares an integer Outputs the type of $testString


1823 print( "$testDouble is a(n) " . gettype( $testDouble )

24 . "<br />" );

25 print( "$testInteger is a(n) " . gettype( $testInteger)

26 . "<br />" );


28 <br />

29 converting to other data types:<br />

30 <?php

31 // call function settype to convert variable

32 // testString to different data types

33 print( "$testString" );

34 settype( $testString, "double" ); 35 print( " as a double is $testString <br />" ); 36 print( "$testString" );

37 settype( $testString, "integer" ); 38 print( " as an integer is $testString <br />" ); 39 settype( $testString, "string" );

40 print( "converting back to a string results in

41 $testString <br /><br />" );

42

Outline

data.php

(2 of 3)

Modifies $testString to be a double

Modifies $testString to be an integer

Modifies $testString to be a string


1943 // use type casting to cast variables to a different type

44 $data = "98.6 degrees";

45 print( "before casting, $data is a " .

46 gettype( $data ) . "<br /><br />" );

47 print( "using type casting instead: <br />

48 as a double: " . (double) $data .

49 "<br />as an integer: " . (integer) $data );

50 print( "<br /><br />after casting, $data is a " .

51 gettype( $data ) );


53 </body>

54 </html>

Outline

data.php

(3 of 3)

Temporarily casts $data as a double and an integer

Concatenation


20Error-Prevention Tip 23.1

Function print can be used to displaythe value of a variable at a particularpoint during a program’s execution.

This is often helpful in debugging a script.


2123.2 PHP Basics (Cont.)

Function define creates a named constant. It takes two arguments—the name and value of the

constant. Line 17 of Fig.23.4 An optional third argument accepts a boolean value that

specifies whether the constant is case insensitive – constants are case sensitive by default.

Uninitialized variables have the value undef, which has different values, depending on its context. In a numeric context, it evaluates to 0. In a string context, it evaluates to an empty string ("").

Keywords may not be used as identifiers.



Assigning a value to a constant afterit is declared is a syntax error.


23 1 <?php print( '<?xml version = "1.0" encoding = "utf-8"?>' ) ?> 2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" 3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 4

5  6  7 <html xmlns = "http://www.w3.org/1999/xhtml"> 8 <head> 9 <title>Using arithmetic operators</title> 10 </head> 11 <body> 12 <?php 13 $a = 5; 14 print( "The value of variable a is $a <br />" ); 15

16 // define constant VALUE 17 define( "VALUE", 5 ); 18

19 // add constant VALUE to variable $a 20 $a = $a + VALUE; 21 print( "Variable a after adding constant VALUE 22 is $a <br />" ); 23

24 // multiply variable $a by 2 25 $a *= 2; 26 print( "Multiplying variable a by 2 yields $a <br />" ); 27

Outline

operators.php

(1 of 3)

Creates the named constant VALUE with a value of 5

Equivalent to $a = $a * 2


2428 // test if variable $a is less than 50 29 if ( $a < 50 ) 30 print( "Variable a is less than 50 <br />" ); 31

32 // add 40 to variable $a 33 $a += 40; 34 print( "Variable a after adding 40 is $a <br />" ); 35

36 // test if variable $a is 50 or less 37 if ( $a < 51 ) 38 print( "Variable a is still 50 or less<br />" ); 39

40 // test if variable $a is between 50 and 100, inclusive 41 elseif ( $a < 101 ) 42 print( "Variable a is now between 50 and 100, 43 inclusive<br />" ); 44 else 45 print( "Variable a is now greater than 100 <br />" ); 46

47 // print an uninitialized variable 48 print( "Using a variable before initializing: 49 $nothing <br />" ); // nothing evaluates to "" 50

51 // add constant VALUE to an uninitialized variable 52 $test = $num + VALUE; // num evaluates to 0

Outline

operators.php

(2 of 3)Uses a comparison operator with a variable and an integer

Uninitialized variable $num evaluates to 0


2553 print( "An uninitialized variable plus constant

54 VALUE yields $test <br />" );

55

56 // add a string to an integer

57 $str = "3 dollars";

58 $a += $str;

59 print( "Adding a string to variable a yields $a <br />" );


61 </body>

62 </html>

Outline

operators.php

(3 of 3)

$str is converted to an integer for this operation



Initialize variables before they are usedto avoid subtle errors.

For example, multiplying a number by an uninitialized variable results in 0.


27

PHP keywords

abstract die exit interface require and do extends isset require_once array echo __FILE__ __LINE__ return as else file line static break elseif final list switch case empty for __METHOD__ throw catch enddeclare foreach method try __CLASS__ endfor __FUNCTION__ new unset

class endforeach function or use clone endif global php_user_filter var

const endswitch if print while continue endwhile implements private xor declare eval include protected default exception include_once public

Fig. 23.5 | PHP keywords.


2823.2 PHP Basics (Cont.) PHP provides the capability to store data in arrays. Arrays are divided into elements that behave as individual variables. Array names, like other variables, begin with the $ symbol.

Individual array elements are accessed by following the array’s variable name with an index enclosed in square brackets ([]).

If a value is assigned to an array that does not exist, then the array is created. Likewise, assigning a value to an element where the index is omitted appends a new element to the end of the array.

Function count returns the total number of elements in the array.

Function array creates an array that contains the arguments passed to it. The first item in the argument list is stored as the first array element (index 0),

the second item is stored as the second array element and so on.


2923.2 PHP Basics (Cont.) Arrays with nonnumeric indices are called associative arrays. You can create an

associative array using the operator =>, where the value to the left of the operator is the array index and the value to the right is the element’s value.

PHP provides functions for iterating through the elements of an array. Each array has a built-in internal pointer, which points to the array element

currently being referenced.

Function reset sets the internal pointer to the first array element. Function key returns the index of the element currently referenced by the internal

pointer, and function next moves the internal pointer to the next element.

The foreach statement, designed for iterating through arrays, starts with the array to iterate through, followed by the keyword as, followed by two variables—the first is assigned the index of the element and the second is assigned the value of that index’s element. (If only one variable is listed after as, it is assigned the value of the array element.)

foreach ( $fourth as $element => $value )

print( "$element is the $value month <br />" );



5  6  7 <html xmlns = "http://www.w3.org/1999/xhtml"> 8 <head> 9 <title>Array manipulation</title> 10 </head> 11 <body> 12 <?php 13 // create array first 14 print( "<strong>Creating the first array</strong><br />" ); 15 $first[ 0 ] = "zero"; 16 $first[ 1 ] = "one"; 17 $first[ 2 ] = "two"; 18 $first[] = "three"; 19

20 // print each element’s index and value 21 for ( $i = 0; $i < count( $first ); $i++ ) 22 print( "Element $i is $first[$i] <br />" ); 23

Outline

arrays.php

(1 of 4)

Sets the first element of array $first to the string “zero”

Automatically creates array $first

“three” is appended to the end of array $first

Returns the number of elements in the array


3124 print( "<br /><strong>Creating the second array

25 </strong><br />" );

26

27 // call function array to create array second

28 $second = array( "zero", "one", "two", "three" );

29

30 for ( $i = 0; $i < count( $second ); $i++ )

31 print( "Element $i is $second[$i] <br />" );

32

33 print( "<br /><strong>Creating the third array

34 </strong><br />" );

35

36 // assign values to entries using nonnumeric indices

37 $third[ "Amy" ] = 21;

38 $third[ "Bob" ] = 18;

39 $third[ "Carol" ] = 23;

40

41 // iterate through the array elements and print each

42 // element’s name and value

43 for ( reset( $third ); $element = key( $third ); next( $third ) )

44 print( "$element is $third[$element] <br />" );

45

Outline

arrays.php

(2 of 4)

Function array creates array $second with its arguments as elements

Creates associative array $third

Sets the internal pointer to the first array element in $third

Returns the index of the element being pointed to;

When function cannot return an index => $element = false

Moves the internal pointer to the next element and returns it;

returns false when there are no more elements in the array


3246 print( "<br /><strong>Creating the fourth array

47 </strong><br />" );

48

49 // call function array to create array fourth using

50 // string indices

51 $fourth = array(

52 "January" => "first", "February" => "second",

53 "March" => "third", "April" => "fourth",

54 "May" => "fifth", "June" => "sixth",

55 "July" => "seventh", "August" => "eighth",

56 "September" => "ninth", "October" => "tenth",

57 "November" => "eleventh","December" => "twelfth"

58 );

59

60 // print each element’s name and value

61 foreach ( $fourth as $element => $value )

62 print( "$element is the $value month <br />" );


64 </body>

65 </html>

Outline

Uses operator => to initialize the element with index “January” to have value “first”

Iterates through each element in array $fourth

Stores the index of the element

Stores the value of the element


33

Outline

arrays.php

(4 of 4)


3423.3 String Processing and Regular Expressions

A regular expression is a series of characters used for pattern-matching templates in strings, text files and databases.

Many string-processing tasks can be accomplished using the equality and relational operators (==, !=, <, <=, > and >=).

Function strcmp compares two strings. The function returns -1 if the first string alphabetically precedes the second string, 0 if the strings are equal, and 1 if the first string alphabetically follows the second.





4

5 

6 


8 <head>

9 <title>String Comparison</title>

10 </head>

11 <body>

12 <?php

13 // create array fruits

14 $fruits = array( "apple", "orange", "banana" );

15

16 // iterate through each array element

17 for ( $i = 0; $i < count( $fruits ); $i++ )

18 {

19 // call function strcmp to compare the array element

20 // to string "banana"

21 if ( strcmp( $fruits[ $i ], "banana" ) < 0 )

22 print( $fruits[ $i ] . " is less than banana " );

23 elseif ( strcmp( $fruits[ $i ], "banana" ) > 0 )

24 print( $fruits[ $i ] . " is greater than banana " );

25 else

26 print( $fruits[ $i ] . " is equal to banana " );

27

28 // use relational operators to compare each element

29 // to string "apple"

Outline

compare.php

(1 of 2)

Checks whether the ith element of the fruits array preceeds the string banana


3630 if ( $fruits[ $i ] < "apple" )

31 print( "and less than apple! <br />" );

32 elseif ( $fruits[ $i ] > "apple" )

33 print( "and greater than apple! <br />" );

34 elseif ( $fruits[ $i ] == "apple" )

35 print( "and equal to apple! <br />" );

36 } // end for


38 </body>

39 </html>

Outline

compare.php

(2 of 2)

Uses relational operators to compare the element of the fruits array with the string apple


3723.3 String Processing and Regular Expressions (Cont.)

Goal: find pattern in text Regular expression (as ereg ) – specially formated strings used to find patterns in

text

Functions ereg and preg_match use regular expressions to search a string for a specified pattern.

If a pattern is found using ereg, it returns the length of the matched first string-which evaluates to true in a boolean context.

Function ereg receives a regular expression pattern to search for and the string to search.

The optional third argument to function ereg is an array that stores matches to each parenthetical statement of the regular expression. The first element stores the string matched for the entire pattern, and the remaining elements are indexed from left to right.

Function eregi performs case-insensitive pattern matches.

To find multiple instances of a given pattern, we must make multiple calls to ereg, and remove matched instances before calling the function again by using a function such as ereg_replace.



Anything enclosed in single quotes in a print statement is not interpolated (unless the single quotes are nested in a double-quoted string literal).

Regular expressions can include metacharacters that specify patterns. the caret (^) metacharacter matches the beginning of a string, while the dollar sign ($) matches the end of a string. the period (.) metacharacter matches any single character.

Bracket expressions are lists of characters enclosed in square brackets ([]) that match any single character from the list. Ranges can be specified by supplying the beginning and the end of the range separated by a dash (-).

ex: [a-zA-Z]

The special bracket expressions [[:<:]] and [[:>:]] match the beginning and end of a word, respectively.

Quantifiers are used in regular expressions to denote how often a particular character or set of characters can appear in a match.



A character class represents a group of characters that might appear in a string ex. [[:alpha:]]

Character classes, or sets of specific characters, are enclosed by the delimiters [: and :]. When this expression is placed in another set of brackets, it is a

regular expression matching all of the characters in the class.

A bracketed expression containing two or more adjacent character classes in the class delimiters represents those character sets combined.

Function ereg_replace takes 3 arguments—the pattern to match, a string to replace the matched string and the string to search. The modified string is returned.


40

Quantifier Matches

{n} Exactly n times.

{m,n} Between m and n times, inclusive.

{n,} n or more times.

+ One or more times (same as {1,}).

* Zero or more times (same as {0,}).

? Zero or one time (same as {0,1}).

Fig. 23.9 | Some PHP quantifiers.


41

Character class Description

alnum Alphanumeric characters (i.e., letters [a-zA-Z] or digits [0-9]).

alpha Word characters (i.e., letters [a-zA-Z]).

digit Digits.

space White space.

lower Lowercase letters.

upper Uppercase letters.

Fig. 23.10 | Some PHP character classes.





4

5 

6 


8 <head>

9 <title>Regular expressions</title>

10 </head>

11 <body>

12 <?php

13 $search = "Now is the time";

14 print( "Test string is: '$search'<br /><br />" );

15

16 // call ereg to search for pattern 'Now' in variable search

17 if ( ereg( "Now", $search ) )

18 print( "String 'Now' was found.<br />" );

19

20 // search for pattern 'Now' in the beginning of the string

21 if ( ereg( "^Now", $search ) )

22 print( "String 'Now' found at beginning

23 of the line.<br />" );

24

25 // search for pattern 'Now' at the end of the string

26 if ( ereg( "Now$", $search ) )

27 print( "String 'Now' was found at the end

28 of the line.<br />" );

29

Outline

expression.php

(1 of 2)

String to search

Searches for the string “Now” in $search

Checks if string “Now” appears at the beginning of $search

Checks if string “Now” appears at the end of $search


4330 // search for any word ending in 'ow'

31 if ( ereg( "[[:<:]]([a-zA-Z]*ow)[[:>:]]", $search, $match ) )

32 print( "Word found ending in 'ow': " .

33 $match[ 1 ] . "<br />" );

34

35 // search for any words beginning with 't'

36 print( "Words beginning with 't' found: ");

37

38 while ( eregi( "[[:<:]](t[[:alpha:]]+)[[:>:]]",

39 $search, $match ) )

40 {

41 print( $match[ 1 ] . " " );

42

43 // remove the first occurrence of a word beginning

44 // with 't' to find other instances in the string

45 $search = ereg_replace( $match[ 1 ], "", $search );

46 } // end while


48 </body>

49 </html>

Outline

expression.php

(2 of 2)

Searches for a word ending in “ow” and stores matches in $match array

Quantifier * matches the preceding pattern 0 or more times

$match[0] stores the string matches for the entire pattern

Prints first $match[1] encountered instance of word ending in “ow”;

Second encountered instance of word ending in “ow” will be in $match[2]

Performs a case-insensitive search for words beginning with the letter “t” and then [[:alpha:]]+ i.e. [a-zA-Z]).

Replaces the found instance from the previous call to eregi with an empty string so that the next instance of the pattern can be found and stored in $match

Function ereg_replace takes 3 arguments•the pattern to match, •a string to replace the matched string and •the string to search.

The modified string is returned.


4423.4 Form Processing and Business Logic

Superglobal arrays are associative arrays predefined by PHP that hold variables acquired from user input, the environment or the web server and are accessible in any variable scope.

The arrays $_GET and $_POST retrieve information sent to the server by HTTP get and post requests, respectively.

Using method = "post" appends form data to the browser request that contains the protocol and the requested resource’s URL. Scripts located on the web server’s machine can

access the form data sent as part of the request.


45

Variable name Description

$_SERVER Data about the currently running server.

$_ENV Data about the client’s environment.

$_GET Data sent to the server by a get request.

$_POST Data sent to the server by a post request.

$_COOKIE Data contained in cookies on the client’s computer.

$GLOBALS Array containing all global variables.

Fig. 23.11 | Some useful superglobal arrays.


46 1 <?xml version = "1.0" encoding = "utf-8"?> 2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" 3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 4

5  6  7 <html xmlns = "http://www.w3.org/1999/xhtml"> 8 <head> 9 <title>Sample form to take user input in XHTML</title> 10 <style type = "text/css"> 11 .prompt { color: blue; 12 font-family: sans-serif; 13 font-size: smaller } 14 </style> 15 </head> 16 <body> 17 <h1>Sample Registration Form</h1> 18 <p>Please fill in all fields and click Register.</p> 19

20  21 <form method = "post" action = "form.php"> 22 <div> 23 <img src = "images/user.gif" alt = "User" /><br /> 24 <span class = "prompt"> 25 Please fill out the fields below.<br /> 26 </span> 27

Outline

form.html

(1 of 4)

Appends form data to the browser request that contains the protocol and the URL of the requested resource

Form data is posted to form.php to be processed


4728 

29 <img src = "images/fname.gif" alt = "First Name" />

30 <input type = "text" name = "fname" /><br />

31

32 <img src = "images/lname.gif" alt = "Last Name" />

33 <input type = "text" name = "lname" /><br />

34

35 <img src = "images/email.gif" alt = "Email" />

36 <input type = "text" name = "email" /><br />

37

38 <img src = "images/phone.gif" alt = "Phone" />

39 <input type = "text" name = "phone" /><br />

40

41 <span style = "font-size: 10pt">

42 Must be in the form (555)555-5555</span>

43 <br /><br />

44

45 <img src = "images/downloads.gif"

46 alt = "Publications" /><br />

47

48 <span class = "prompt">

49 Which book would you like information about?

50 </span><br />

51

52 

53 <select name = "book">

Outline

form.html

(2 of 4)

Creates form fields

Creates drop-down list with book names


4854 <option>Internet and WWW How to Program 4e</option>

55 <option>C++ How to Program 6e</option>

56 <option>Java How to Program 7e</option>

57 <option>Visual Basic 2005 How to Program 3e</option>

58 </select>

59 <br /><br />

60

61 <img src = "images/os.gif" alt = "Operating System" />

62 <br /><span class = "prompt">

63 Which operating system are you currently using?

64 <br /></span>

65

66 

67 <input type = "radio" name = "os" value = "Windows XP"

68 checked = "checked" /> Windows XP

69 <input type = "radio" name = "os" value =

70 "Windows Vista" /> Windows Vista<br />

71 <input type = "radio" name = "os" value =

72 "Mac OS X" /> Mac OS X

73 <input type = "radio" name = "os" value = "Linux" /> Linux

74 <input type = "radio" name = "os" value = "Other" /> Other

75 <br />

76

Outline

form.html

(3 of 4)

Creates radio buttons with “Windows XP” initially selected


4977 

78 <input type = "submit" value = "Register" />

79 </div>

80 </form>

81 </body>

82 </html>

Outline

form.html

(4 of 4)


50Good Programming Practice 23.1

Use meaningful XHTML object names for input fields.

This makes PHP scripts that retrieve form data easier to understand.


5123.4 Form Processing and Business Logic (Cont.)

Function extract creates a variable/value pair corresponding to each key/value pair in the associative array passed as an argument.

Business logic, or business rules, ensures that only valid information is stored in databases.

We escape the normal meaning of a character in a string by preceding it with the backslash character (\).

Function die terminates script execution. The function’s optional argument is a string, which is printed as the script exits.



5  6  7 <html xmlns = "http://www.w3.org/1999/xhtml"> 8 <head> 9 <title>Form Validation</title> 10 <style type = "text/css"> 11 body { font-family: arial, sans-serif } 12 div { font-size: 10pt; 13 text-align: center } 14 table { border: 0 } 15 td { padding-top: 2px; 16 padding-bottom: 2px; 17 padding-left: 10px; 18 padding-right: 10px } 19 .error { color: red } 20 .distinct { color: blue } 21 .name { background-color: #ffffaa } 22 .email { background-color: #ffffbb } 23 .phone { background-color: #ffffcc } 24 .os { background-color: #ffffdd } 25 </style> 26 </head> 27 <body>

Outline

form.php

(1 of 5)


5328 <?php 29 extract( $_POST ); 30

31 // determine whether phone number is valid and print 32 // an error message if not 33 if ( !ereg( "^$[0-9]{3}$[0-9]{3}-[0-9]{4}$", $phone ) ) 34 { 35 print( "<p><span class = 'error'> 36 Invalid phone number</span><br /> 37 A valid phone number must be in the form 38 <strong>(555)555-5555</strong><br /> 39 <span class = 'distinct'> 40 Click the Back button, enter a valid phone 41 number and resubmit.<br /><br /> 42 Thank You.</span></p>" ); 43 die( "</body></html>" ); // terminate script execution 44 } 45 ?> 46 <p>Hi 47 <span class = "distinct"> 48 <strong><?php print( "$fname" ); ?></strong> 49 </span>. 50 Thank you for completing the survey.<br /> 51 You have been added to the 52 <span class = "distinct"> 53 <strong><?php print( "$book " ); ?></strong> 54 </span> 55 mailing list.

Creates a variable/value pair for each key/value pair in $_POST

Ensures that phone number is in proper format

Terminates execution and closes the document properly


5456 </p> 57 <p><strong>The following information has been saved 58 in our database:</strong></p> 59 <table> 60 <tr> 61 <td class = "name">Name </td> 62 <td class = "email">Email</td> 63 <td class = "phone">Phone</td> 64 <td class = "os">OS</td> 65 </tr> 66 <tr> 67 <?php 68 // print each form field’s value 69 print( "<td>$fname $lname</td> 70 <td>$email</td> 71 <td>$phone</td> 72 <td>$os</td>" ); 73 ?> 74 </tr> 75 </table> 76 <br /><br /><br /> 77 <div>This is only a sample form. 78 You have not been added to a mailing list.</div> 79 </body> 80 </html>

Outlineform.php

(3 of 5)

Prints the value entered in the email field in form.html


55

Outline

form.php

(4 of 5)


56

Outline

form.php

(5 of 5)


57Software Engineering Observation 23.1

Use business logic to ensure that invalid information is not stored in databases.

When possible, validate important or sensitive

form data on the server, since JavaScript may be disabled by the client. Some data, such as passwords, must always be

validated on the server side.



Be sure to close any open XHTML tags when calling function die.

Not doing so can produce invalid XHTML output that will not display properly in the client browser.

Function die has an optional parameter that specifies a message to output when exiting, so one technique for closing tags is to close all open tags using die, as in die("</body></html>").


5923.5 Connecting to a Database Function mysql_connect connects to the MySQL database. It takes three arguments— the server’s hostname, a username and a password, and returns a database handle - a representation of PHP’s connection to the database,

or false if the connection fails.

Function mysql_select_db specifies the database to be queried, and returns a bool indicating whether or not it was successful.

To query the database, we call function mysql_query, specifying the query string and the database to query.

This returns a resource containing the result of the query, or false if the query fails.

It can also execute SQL statements such as INSERT or DELETE that do not return results.

Function mysql_error returns any error strings from the database. mysql_close closes the connection to the database specified in its argument.


60 1 <?xml version = "1.0" encoding = "utf-8"?>



4

5 

6 


8 <head>

9 <title>Sample Database Query</title>

10 <style type = "text/css">

11 body { background-color: #F0E68C }

12 h2 { font-family: arial, sans-serif;

13 color: blue }

14 input { background-color: blue;

15 color: yellow;

16 font-weight: bold }

17 </style>

18 </head>

19 <body>

20 <h2> Querying a MySQL database.</h2>

21 <form method = "post" action = "database.php">

22 <div>

23 <p>Select a field to display:

24 

25 

Outline

data.html

(1 of 2)

Posts data to database.php


6126 <select name = "select">

27 <option selected = "selected">*</option>

28 <option>ID</option>

29 <option>Title</option>

30 <option>Category</option>

31 <option>ISBN</option>

32 </select></p>

33 <input type = "submit" value = "Send Query" />

34 </div>

35 </form>

36 </body>

37 </html>

Outline

data.html

(2 of 2)

Creates drop-down menu specifying which data to output to the screen, with * (all data) as the default selection



5  6  7 <html xmlns = "http://www.w3.org/1999/xhtml"> 8 <head> 9 <title>Search Results</title> 10 <style type = "text/css"> 11 body { font-family: arial, sans-serif; 12 background-color: #F0E68C } 13 table { background-color: #ADD8E6 } 14 td { padding-top: 2px; 15 padding-bottom: 2px; 16 padding-left: 4px; 17 padding-right: 4px; 18 border-width: 1px; 19 border-style: inset } 20 </style> 21 </head> 22 <body> 23 <?php 24 extract( $_POST ); 25

26 // build SELECT query 27 $query = "SELECT " . $select . " FROM books"; 28

Outline

database.php

(1 of 3)

Builds a SELECT query with the selection made in data.html


6329 // Connect to MySQL

30 if ( !( $database = mysql_connect( "localhost",

31 "iw3htp4", "iw3htp4" ) ) )

32 die( "Could not connect to database </body></html>" );

33

34 // open Products database

35 if ( !mysql_select_db( "products", $database ) )

36 die( "Could not open products database </body></html>" );

37

38 // query Products database

39 if ( !( $result = mysql_query( $query, $database ) ) )

40 {

41 print( "Could not execute query! <br />" );

42 die( mysql_error() . "</body></html>" );

43 } // end if

44

45 mysql_close( $database );


47 <h3>Search Results</h3>

48 <table>

49 <?php

50 // fetch each record in result set

51 for ( $counter = 0; $row = mysql_fetch_row( $result );

52 $counter++ )

53 {

54 // build table to display results

55 print( "<tr>" );

56

Outline

database.php

(2 of 3)

Connects to database using server hostname localhost and username and password “iw3htp4”

Specifies products as the database to be queried

Queries $database with $query

Returns any error strings from the database

Closes the connection to the database

Returns an array with the values for each column of the current row in $result


6457 foreach ( $row as $key => $value )

58 print( "<td>$value</td>" );

59

60 print( "</tr>" );

61 } // end for


63 </table>

64 <br />Your search yielded <strong>

65 <?php print( "$counter" ) ?> results.<br /><br /></strong>

66 <h5>Please email comments to

67 <a href = "mailto:[email protected]">

68 Deitel and Associates, Inc.</a>

69 </h5>

70 </body>

71 </html>

Outline

database.php

(3 of 3)

"$counter“ has the # of rows;

The same as mysql_num_rows($result)


6523.6 Using Cookies A cookie is a text file that a website stores on a client’s computer to maintain

information about the client during and between browsing sessions.

A server can access only the cookies that it has placed on the client.

Function setcookie takes the name of the cookie to be set as the first argument, followed by the value to be stored in the cookie. The optional third argument indicates the expiration date of the cookie. A cookie without a third argument is known as a session cookie, while one

with an expiration date is a persistent cookie. If only the name argument is passed to function setcookie, the cookie is

deleted from the client’s computer.

Cookies defined in function setcookie are sent to the client at the same time as the information in the HTTP header; therefore, it needs to be called before any XHTML is printed.

The current time is returned by function time.


66 1 <?xml version = "1.0" encoding = "utf-8"?>



4

5 

6 


8 <head>

9 <title>Writing a cookie to the client computer</title>


11 body { font-family: arial, sans-serif;

12 background-color: #99CCFF }

13 form { font-size: 10pt }

14 .submit { background-color: #F0E86C;

15 color: navy;

16 font-weight: bold }

17 </style>

18 </head>

19 <body>

20 <h2>Click Write Cookie to save your cookie data.</h2>

21 <form method = "post" action = "cookies.php">

22 <div>

23 <strong>Name:</strong><br />

24 <input type = "text" name = "Name" /><br />

25

26 <strong>Height:</strong><br />

27 <input type = "text" name = "Height" /><br />

28

Outlinecookies.html (1 of 2)

Posts form data to cookies.php

Creates fields to gather information to be written into a cookie


6729 <strong>Favorite Color:</strong><br />

30 <input type = "text" name = "Color" /><br />

31

32 <input type = "submit" value = "Write Cookie"

33 class = "submit" />

34 </div>

35 </form>

36 </body>

37 </html>

Outline

cookies.html(2 of 2)

Form field


68 1 <?php 2 // Fig. 23.17: cookies.php 3 // Writing a cookie to the client. 4 extract( $_POST ); 5

6 // write each form field’s value to a cookie and set the 7 // cookie’s expiration date 8 setcookie( "Name", $Name, time() + 60 * 60 * 24 * 5 ); 9 setcookie( "Height", $Height, time() + 60 * 60 * 24 * 5 ); 10 setcookie( "Color", $Color, time() + 60 * 60 * 24 * 5 ); 11 ?> 12

13 <?php print( '<?xml version = "1.0" encoding = "utf-8"?>' ) ?> 14 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" 15 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 16

17 <html xmlns = "http://www.w3.org/1999/xhtml"> 18 <head> 19 <title>Cookie Saved</title> 20 <style type = "text/css"> 21 body { font-family: arial, sans-serif } 22 span { color: blue } 23 </style> 24 </head> 25 <body> 26 <p>The cookie has been set with the following data:</p> 27

28  29 <br /><span>Name:</span><?php print( $Name ) ?><br />

Outline

cookies.php

(1 of 2)

Creates a cookie for each entered value and sets the expiration date to be five days after the current time


6930 <span>Height:</span><?php print( $Height ) ?><br />

31 <span>Favorite Color:</span>

32 <span style = "color: <?php print( "$Color\">$Color" ) ?>

33 </span><br />

34 <p>Click <a href = "readCookies.php">here</a>

35 to read the saved cookie.</p>

36 </body>

37 </html>

Outline

cookies.php

(2 of 2)

Links to the page that displays the contents of the cookie


70Software Engineering Observation 23.2 - 3

Some clients do not accept cookies.

When a client declines a cookie, the browser application normally informs the user thatthe site may not function correctly without cookies enabled.

Cookies should not be used to storee-mail addresses or private data on aclient’s computer.


7123.6 Using Cookies (Cont.)

When using Internet Explorer, cookies are stored in a Cookies directory on the client’s machine.

In Firefox, cookies are stored in a file named cookies.txt.


72

Fig. 23.18 | IE7’s Cookies directory before a cookie is written.

Fig. 23.19 | IE7’s Cookies directory after a cookie is written.


7323.6 Using Cookies (Cont.)

PHP creates the superglobal array $_COOKIE, which contains all the cookie values indexed by their names.



5  6  7 <html xmlns = "http://www.w3.org/1999/xhtml"> 8 <head> 9 <title>Read Cookies</title> 10 <style type = "text/css"> 11 body { font-family: arial, sans-serif } 12 table { border-width: 5px; 13 border-style: outset } 14 td { padding: 10px } 15 .key { background-color: #F0E68C } 16 .value { background-color: #FFA500 } 17 </style> 18 </head> 19 <body> 20 <p> 21 <strong>The following data is saved in a cookie on your 22 computer.</strong> 23 </p> 24 <table> 25 <?php 26 // iterate through array $_COOKIE and print 27 // name and value of each cookie

Outline

readCookies.php

(1 of 2)


7528 foreach ( $_COOKIE as $key => $value )

29 print( "<tr><td class = 'key' >$key</td>

30 <td class = 'value' >$value</td></tr>" );


32 </table>

33 </body>

34 </html>

Outline

readCookies.php

(2 of 2)

Iterates through all values in $_COOKIE


7623.7 Dynamic Content

Function isset allows you to find out if a variable has a value.

A variable ($$variable) allows the code to reference variables dynamically.

You can use this expression to obtain the value of the variable whose name is equal to the value of $variable.

The quotemeta function inserts a backslash (\) before any special characters in the passed string.





4 // must use form.html from Fig.23.13

5 

6 


8 <head>

9 <title>Sample form to take user input in XHTML</title>


11 td { padding-top: 2px;

12 padding-bottom: 2px;

13 padding-left: 10px;

14 padding-right: 10px }

15 div { text-align: center }

16 div div { font-size: larger }

17 .name { background-color: #ffffaa }

18 .email { background-color: #ffffbb }

19 .phone { background-color: #ffffcc }

20 .os { background-color: #ffffdd }

21 .smalltext { font-size: smaller }

22 .prompt { color: blue;

23 font-family: sans-serif;

24 font-size: smaller }

25 .largeerror { color: red }

26 .error { color: red;

27 font-size: smaller }

28 </style>

29 </head>

Outline

dynamicForm.php

(1 of 12)


7830 <body> 31 <?php 32 extract( $_POST ); 33 $iserror = false; 34

35 // array of book titles 36 $booklist = array( "Internet and WWW How to Program 4e", 37 "C++ How to Program 6e", "Java How to Program 7e", 38 "Visual Basic 2005 How to Program 3e" ); 39

40 // array of possible operating systems 41 $systemlist = array( "Windows XP", "Windows Vista", 42 "Mac OS X", "Linux", "Other"); 43

44 // array of name values for the text input fields 45 $inputlist = array( "fname" => "First Name", 46 "lname" => "Last Name", "email" => "Email", 47 "phone" => "Phone" ); 48

49 // ensure that all fields have been filled in correctly 50 if ( isset ( $submit ) ) 51 { 52 if ( $fname == "" ) 53 { 54 $formerrors[ "fnameerror" ] = true; 55 $iserror = true; 56 } // end if 57

OutlinedynamicForm.php

(2 of 12)

Checks whether the Register button has been pressed

Checks that the first name field is not blank

Makes an entry in the error array

Sets $iserror to true


7958 if ( $lname == "" )

59 {

60 $formerrors[ "lnameerror" ] = true;

61 $iserror = true;

62 } // end if

63

64 if ( $email == "" )

65 {

66 $formerrors[ "emailerror" ] = true;

67 $iserror = true;

68 } // end if

69 70 //if ( !ereg( "^$[0-9]{3}$[0-9]{3}-[0-9]{4}$", $phone ) ) - deprecated; error if ( !preg_match( "/^$[0-9]{3}$[0-9]{3}-[0-9]{4}$/", $phone ) ) 71 {

72 $formerrors[ "phoneerror" ] = true;

73 $iserror = true;

74 } // end if

75

76 if ( !$iserror )

77 {

78 // build INSERT query

79 $query = "INSERT INTO contacts " .

80 "( LastName, FirstName, Email, Phone, Book, OS ) " .

81 "VALUES ( '$lname', '$fname', '$email', " .

82 "'" . quotemeta( $phone ) . "', '$book', '$os' )";

Outline

dynamicForm.php

(3 of 12)

Checks that all other form fields are filled in correctly

Inserts a backslash before the parentheses in the phone number


8083

84 // Connect to MySQL

85 if ( !( $database = mysql_connect( "localhost",

86 "iw3htp4", "iw3htp4" ) ) )

87 die( "Could not connect to database" );

88

89 // open MailingList database 90 if ( !mysql_select_db( "MailingList", $database ) ) //JG error lower cases 91 die( "Could not open MailingList database" );

92

93 // execute query in MailingList database

94 if ( !( $result = mysql_query( $query, $database ) ) )

95 {

96 print( "Could not execute query! <br />" );

97 die( mysql_error() );

98 } // end if

99


101

102 print( "<p>Hi<span class = 'prompt'>

103 <strong>$fname</strong></span>.

104 Thank you for completing the survey.<br />

105

106 You have been added to the

107 <span class = 'prompt'>

108 <strong>$book</strong></span>

109 mailing list.</p>

110 <strong>The following information has been saved

111 in our database:</strong><br />

112

Outline

dynamicForm.php

(4 of 12)


81113 <table><tr> 114 <td class = 'name'>Name </td> 115 <td class = 'email'>Email</td> 116 <td class = 'phone'>Phone</td> 117 <td class = 'os'>OS</td> 118 </tr><tr> 119

120  121 <td>$fname $lname</td> 122 <td>$email</td> 123 <td>$phone</td> 124 <td>$os</td> 125 </tr></table> 126

127 <br /><br /><br /> 128 <div><div> 129 <a href = 'formDatabase.php'> 130 Click here to view entire database.</a> 131 </div>This is only a sample form. 132 You have not been added to a mailing list. 133 </div></body></html>" ); 134 die(); 135 } // end if 136 } // end if 137

138 print( "<h1>Sample Registration Form.</h1> 139 Please fill in all fields and click Register." ); 140

Outline

dynamicForm.php

(5 of 12)

Ends script here if there were no errors in the user input

Section to be executed only if $iserror is true


82141 if ( $iserror )

142 {

143 print( "<br /><span class = 'largeerror'>

144 Fields with * need to be filled in properly.</span>" );

145 } // end if

146

147 print( "

148 <form method = 'post' action = 'dynamicForm.php'>

149 <img src = 'images/user.gif' alt = 'User' /><br />


151 Please fill out the fields below.<br /> </span>

152

153 " );

154 foreach ( $inputlist as $inputname => $inputalt )

155 {

156 $inputtext = $inputvalues[ $inputname ]; // JG remove – not used

157

158 print( "<img src = 'images/$inputname.gif'

159 alt = '$inputalt' /><input type = 'text'

160 name = '$inputname' value = '" . $$inputname . "' />" );

161

162 if ( $formerrors[ ( $inputname )."error" ] == true )

163 print( "<span class = 'error'>*</span>" );

164

165 print( "<br />" );

166 } // end foreach

167

168 if ( $formerrors[ "phoneerror" ] )

169 print( "<span class = 'error'>" );

Outline

dynamicForm.php

(6 of 12)

Alerts the user that there are errors

Iterates through $inputlist to create the form’s text boxes

Outputs the field’s image

Sets the name attribute of the text field to $inputname

Sets the value attribute of the text field to the value of the variable with the name of $inputname’s value

Puts an asterisk next to fields that have errors


83170 else

171 print("<span class = 'smalltext'>");

172

173 print( "Must be in the form (555)555-5555

174 </span><br /><br />

175

176 <img src = 'images/downloads.gif'

177 alt = 'Publications' /><br />

178


180 Which book would you like information about?

181 </span><br />

182

183 

184 <select name = 'book'>" );

185

186 foreach ( $booklist as $currbook )

187 {

188 print( "<option" );

189

190 if ( ( $currbook == $book ) )

191 print( " selected = 'true'" );

192

193 print( ">$currbook</option>" );

194 } // end foreach

195

Outline

dynamicForm.php

(7 of 12)

Creates drop-down list for books, keeping the previously selected one selected


84196 print( "</select><br /><br /> 197 <img src = 'images/os.gif' alt = 'Operating System' /> 198 <br /><span class = 'prompt'> 199 Which operating system are you currently using? 200 <br /></span> 201

202 " ); 203

204 $counter = 0; 205

206 foreach ( $systemlist as $currsystem ) 207 { 208 print( "<input type = 'radio' name = 'os' 209 value = '$currsystem'" ); 210

211 if ( $currsystem == $os ) 212 print( "checked = 'checked'" ); 213 elseif ( !$os && $counter == 0 ) 214 print( "checked = 'checked'" ); 215

216 print( " />$currsystem" ); 217

218 // put a line break in list of operating systems 219 if ( $counter == 1 ) print( "<br />" ); 220 ++$counter; 221 } // end foreach 222

Outline

dynamicForm.php

(8 of 12)

Creates radio buttons for operating-system selection, keeping the previously selected option selected


85223 print( "

224 <br /><input type = 'submit' name = 'submit'

225 value = 'Register' /></form></body></html>" );


Outline

dynamicForm.php

(9 of 12)


86

Outline

dynamicForm.php

(10 of 12)


87

Outline

dynamicForm.php

(11 of 12)


88

Outline

dynamicForm.php

(12 of 12)



5  6  7 <html xmlns = "http://www.w3.org/1999/xhtml"> 8 <head> 9 <title>Search Results</title> 10 <style type = "text/css"> 11 body { font-family: arial, sans-serif; 12 background-color: #F0E68C } 13 h3 { color: blue } 14 table { background-color: #ADD8E6 } 15 td { padding-top: 2px; 16 padding-bottom: 2px; 17 padding-left: 4px; 18 padding-right: 4px; 19 border-width: 1px; 20 border-style: inset } 21 </style> 22 </head> 23 <body> 24 <?php 25 extract( $_POST ); 26

27 // build SELECT query 28 $query = "SELECT * FROM contacts"; 29

Outline

formDatabase.php

(1 of 3)

Selects all fields from the contacts database to display


9030 // Connect to MySQL 31 if ( !( $database = mysql_connect( "localhost", 32 "iw3htp4", "iw3htp4" ) ) ) 33 die( "Could not connect to database </body></html>" ); 34

35 // open MailingList database 36 if ( !mysql_select_db( "MailingList", $database ) ) 37 die( "Could not open MailingList database </body></html>" ); 38

39 // query MailingList database 40 if ( !( $result = mysql_query( $query, $database ) ) ) 41 { 42 print( "Could not execute query! <br />" ); 43 die( mysql_error() . "</body></html>" ); 44 } // end if 45 ?> 46

47 <h3>Mailing List Contacts</h3> 48 <table> 49 <tr> 50 <td>ID</td> 51 <td>Last Name</td> 52 <td>First Name</td> 53 <td>E-mail Address</td> 54 <td>Phone Number</td> 55 <td>Book</td> 56 <td>Operating System</td> 57 </tr> 58 <?php

Outline

formDatabase.php

(2 of 3)


9159 // fetch each record in result set

60 for ( $counter = 0; $row = mysql_fetch_row( $result );

61 $counter++ )

62 {

63 // build table to display results

64 print( "<tr>" );

65

66 foreach ( $row as $key => $value )

67 print( "<td>$value</td>" );

68

69 print( "</tr>" );

70 } // end for

71



74 </table>

75 </body>

76 </html>

Outline

formDatabase.php

(3 of 3)


9223.8 Operator Precedence Chart

The following table contains a list of PHP operators in decreasing order of precedence.


93

Operator Type Associativity

new constructor none

[] subscript right to left

~ ! ++ -- - @

bitwise not not increment

decrement

unary negative

error control

right to left

* / %

multiplication

division

modulus

left to right

+ - .

addition

subtraction

concatenation

left to right

Fig. 23.23 | PHP operator precedence and associativity. (Part 1 of 3.)


94


<<

>>

bitwise shift left

bitwise shift right

left to right

< > <= >=

less than

greater than

less than or equal

greater than or equal

none

== != === !==

equal

not equal

identical

not identical

none

& bitwise AND left to right

^ bitwise XOR left to right

| bitwise OR left to right

&& logical AND left to right

|| logical OR left to right



95


= += -= *= /= &= |= ^= .= <<= >>=

assignment addition assignment subtraction assignment multiplication assignment division assignment bitwise AND assignment bitwise OR assignment bitwise exclusive OR assignment concatenation assignment bitwise shift left assignment bitwise shift right assignment

left to right

and logical AND left to right

xor exclusive OR left to right

or logical OR left to right

, list left to right

Documents

Jozef Goetz contribution, 2011 1 Credits: Parts of the slides are based on slides created by textbook authors, P.J. Deitel and H. M. Deitel by Prentice