V 1.0 OE NIK 2013 1 PHP+SQL 2. PHP Introduction Control structures, operators Functions Practice ,

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PHP+SQL2.

PHP IntroductionControl structures, operatorsFunctionsPractice

www.w3schools.com,http://www.tizag.com/phpT/index.php

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PHP+SQL2.


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PHP• PHP = „PHP: Hypertext

Preprocessor” („recursive acronym” : GNU, LAME, WINE)

• Serverside programming language

• In a .php file, we can mix HTML code/text and PHP code – we will try to avoid heavily mixing those

• The output is typically HTML code (but it can be anything)

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Server side?• Request Web server php module source file

parser generate output Web server Reply• The web server (Apache, IIS) handles the HTTP

communication, but parts of the communication (headers, content, error codes) can be changed from the PHP code

• HTTP methods: GET, POST, Connect, Trace, Put, Head• 2 main drawbacks of the HTTP:

– Stateless session management– Insecure HTTPS + coding security:

https://www.owasp.org/index.php/

OWASP_PHP_Security_Project4OE NIK 2013

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parser generate output Web server Reply• In the beginning: interpreter languages, CGI approach.

PHP is still interpreted, but not necessarily CGI• Easy-to-use and easy-to-learn programming language

with VERY loose rules and some strange features "Always code as if the person who ends up maintaining your code is a violent psychopath who knows where you live."

• JSP, ASP – "more professional", better for bigger projects (ORM, MVC, object persistence, cache, team work support, developing tools – PHP is getting better!)

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parser generate output Web server Reply• The parser reads the whole source file, but only the

marked parts are interpreted, the rest is forwarded into the output without any modification

• <html><body> UNPARSED CONTENT, YAY<?phpecho "Hello World ... ";echo 22+20;?><hr> THIS IS HTML TOO </body></html>

• Errrr, what about fatal parser errors?• Notice/warning/error, display_errors vs error_reporting

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PHP vs Javascript

<html><body>

<?phpecho "Hello World";?>

</body></html>

<html><body>

<script type="text/javascript">document.write("Hello World!")</script>

</body></html>

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Installation, LAMP/WAMP/XAMP

• http://users.nik.uni-obuda.hu/szabozs/install/• Linux/Windows, Apache>=2, MySQL>=5, PHP>=5• Use a simplified installer: WAMP,XAMP• Editor: Notepad++

(eclipse/dreamweaver/phpstorm/zend studio/php designer/phped)

• We will not use any OO/MVC frameworks this semester

• During the tests, one may not use: PEAR, Symfony, CodeIgniter, Joomla, Drupal, Wordpress, etc

• During the project: anything, but do X hours of work!8OE NIK 2013

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PHP+SQL2.


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Statements• A program is a sequence of statements• Simple statements

– Declarations, expressions or function calls– Every statement must be closed with a semicolon „ ; ”

• Compound statements– A coherent block of several simple statements– No semicolon at the end– Other names: "block", "code block" it must be

surrounded with { and } characters

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Comments, variables

<html><body><?php//This is a comment

/*This isa commentblock*/?></body></html>

<?php$txt="Hello World!"; // string$x=16; //intecho $txt;echo $x;// $a1 is good// Az $1a and $123 is not!echo (int) ((0.1 + 0.7) * 10); //7!!!!?>

PHP is a LOOSELY TYPED language! (And not a type-less language! The operators will do the typecasting)

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Strings and variables$hello="Hello";$who = "World";echo "Hello!\n"; //Escape sequences!echo "$hello $who!\n";echo "$hellobello $who!\n";echo "{$hello}bello {$who}!\n";echo "The value of \$hello is \"{$hello}\" ";echo 'Hello $who!\n'; // string "as is"echo 'Hello $who!\'\n'; //Only this one is intepreted

• Do not get used to the automatic variable injection (arrays can get tricky) use quotation marks for string specification and curly braces for variable injetion!

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Indirect variable reference• Since it's an interpreter language, it is possible

$name = ’foo’;$$name = ’bar’;echo $foo; // Echoes ’bar’

$name = ’123’; /* 123 should not be a variable's name */$$name = ’456’; echo ${’123’}; // Echoes ’456’

• AVOID! (except some very useful examples )• Because of the interpreter, we could use eval() too –

ALWAYS AVOID!

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Operator Description Example Result

+(vs .)

Addition $x=2; $y=$x+2;

$x=2; $y=$x.2;

4

22

- Subtraction $x=2;5-$x 3

* Multiplication x=4;$x*5 20

/ Division (float) 15/55/2

32.5

% Remainder 5%210%810%2

120

++ Increase $x=5;$x++; $x=6

-- Decrease $x=5;$x--; $x=4

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POST- and PRE-increment• Look out how the icrement is combined with other

statements (echo, indexing, loop conditions)$a = 1; // integer 1, assign it to $aecho $a++; // Echoes : 1, $a is now 2echo ++$a; // Echoes: 3, $a is now 3echo --$a; // Echoes: 2, $a is now 2echo $a--; // Echoes: 2, $a is now 1

• Suggestion: avoid mixing ++ and -- with other statements!

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Post-increment and typecasting

$a = 1; $b=1;$a=$a+$b;$a++;echo $a; // 3

$a = 1; $b=1;$a=$a.$b;$a++;echo $a; // 12

$a="abc";$a++;echo $a; // abd

$a=(int)"abc";$a++;echo $a; // 1

$a=(int)"12abc";$a++;echo $a; // 13

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Operator Description Example

== Equals 5==8 is false

=== Equals AND HAS THE SAME TYPE

5==”5” is true, 5===”5” is false (5=="5a" is true, 5==="5a" is false)

!=, <> Not equals 5!=8 is true

!== Not equals, with type comparison

5!=”5” is false5!==”5” is true

> Bigger than 5>8 is false

< Smaller than 5<8 is true

>= Bigger or equals 5>=8 is false

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Operator Example Meaning

= $x=$y; $x=$y;

+= $x+=$y; $x=$x+$y;

-= $x-=$y; $x=$x-$y;

*= $x*=$y; $x=$x*$y;

/= $x/=$y; $x=$x/$y;

.= $x.=$y; $x=$x.$y;

%= $x%=$y; $x=$x%$y;

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Operator Description Example

&& , and Logical AND (&: bitwise AND)

$x=6; $y=3;(x < 10 && y > 1) is true

|| , or Logical OR (|: bitwise OR)

$x=6; $y=3;($x==5 || $y==5) is false

! Logical NOT $x=6; $y=3; !($x==$y) is true

xor Logical XOR $x=6; $y=3;($x==6) xor ($y==2) is true

&, |, ^, ~ Bitwise AND, OR, XOR, NOT

<< Left Shift (SHL)

>> Right Shift (SHR)

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Other operators• Access operators

• Ternary operator

Operator Expression Meaning

-> x->y Member access (class)

( ) f(x) Function call

[ ] a[x] Extract parts of strings (later)Array indexing (later)

Operator

Expression Meaning

? : x ? y : z If X is true, then the expression evaluates to Y, otherwise it evaluates to Z … PHP sadness: left associative!!!!!!

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IF

<?php$num=rand(10, 100);if ($num%2 == 0) {

echo "Even";} else {

echo "Odd";}

?>

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if (condition) // code to execute if the condition is true

else // code to execute if the condition is false

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ELSEIF• if (condition1)

// code to execute, if condition1 is trueelseif (condition2) // otherwise, code to execute, if condition2 is trueelse // otherwise, the code to execute

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Short-circuit evaluation• An important feature that is used if we connect more

than one logical expressions using the AND/OR (&& / ||) operators

• When using the AND operator (A && B): if the first expression is false, then the second is not evaluated (the result will always be FALSE)

• When using the OR operator (A || B): if the first expression is true, then the second is not evaluated (the result will always be TRUE)

• This is almost always turned on for nearly every programming language (exception: basic, pascal, java)!

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IF

• „if the condition is true” is not strictly a logical true/false expression or comparison! It can be anything that can be interpreted as boolean (due to the automatic typecasting)• In addition, we do not need comparison at all:

$i = 0;if ($i) echo "Testing for TRUE evaluation…";if (!$i) echo "Testing for FALSE evaluation…";

• Some strange oddities can happen...

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if (condition) // code to execute if the condition is true

else // code to execute if the condition is false

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SHORT int(0) int(1) bool(false) bool(true) string(1) "0" string(1) "1"string(4) "some"

string(0) ""

int(0) FALSE Same Equals Equals Equals Equals

int(1) TRUE Same Equals Equals

bool(false) FALSE Equals Same Equals Equals

bool(true) TRUE Equals Same Equals Equals

string(1) "0" FALSE Equals Equals Same

string(1) "1" TRUE Equals Equals Same

string(4) "some" TRUE Equals Equals Same

string(0) "" FALSE Equals Equals Same

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SWITCH

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switch (expression) // expression: usually a variable{case label1: // Code to execute, if $n==label1 break;case label2: // Code to execute, if $n==label2 break;default: // Code to execute for any other values break;}

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SWITCH$x=rand(0,10);switch ($x) {case 0:case 1: echo "Number 0 or 1"; break;case 2: echo "Number 2"; break;case 3: echo "Number 3";case 4: echo "Number 3 or 4";break;default: echo "Some other number";}

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• Unlike in C# (much like in c/c++), we can use fall-through case sections: the statements are executed from the entry point till the first break statement

• Intervals and conditions cannot be used as case labels, only strict values!

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WHILE

• The condition is always a stay-in condition• Look out for infinite loops! max_time_limit ,

ignore_user_abort

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while (condition){ //code to be executed}

do{ // code to be executed}while (condition);

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WHILE• <html>

<body>

<?php$i=1;while($i<=5) { echo "The number is " . $i . "<br />"; $i++; }?>

</body></html>

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FOR

• initialization: Usually set some counter (e.g. $i=0, but it can be any other code)

• condition: Evaluated after every loop. If TRUE, then the loop continues

• increment: Usually a simple $i++ (but it can be any other code)

• WHILE and FOR loops are sometimes inter-changeable

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for (initialization; stay-in condition; increment){ // code to be executed}

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FOR<html><body>

<?phpfor ($i=1; $i<=5; $i++) { echo "The number is " . $i . "<br />"; }?>

</body></html>

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Break / continue$i = 0;while (true) {

if ($i == 10) {break;

}echo $i .”<br>”;$i++;

}for ($i = 0; $i < 10; $i++) {

for ($j = 0; $j < 3; $j++) {if (($j + $i) % 5 == 0) {

break 2; // Both loops}

}}

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for ($i = 0; $i < 10; $i++) {if ($i > 3 && $i < 6) {

continue;}echo $i . ”<br>”;

}

$i=0;do {

$i+=0.1;echo "NUM: {$i}<br>";if ($i>200) break;

} while ($i!=100);

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Empty statement

• Seldomly used– ProcessMessage() {...} //returns boolean– ProcessQueue() { … while (ProcessMessage()) ; … }– Dangerous! Must be used with caution!

• Common mistake:if (condition) ; // or: while (condition) ;{

// do something}

;

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PHP+SQL2.


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Pre-defined functions• php.net/function_name• var_dump($mixed) , print_r($mixed)• isset($mixed) , unset($mixed), is_numeric($mixed), etc...• round($num), ceil($num), floor($num), rand($min,

$max)• strtolower($str) , strlen($str) , strpos($haystack,

$needle), strcmp($str1, $str2), substr($start, $end, $length) [negative numbers as parameter!] substr, strpos and $str[] indexes the BYTES (vs mb_*)

• date($format)• header($string), serialize($mixed), unserialize($str)• include($filename), include_once($filename),

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Custom functions• function myFunc() {

echo ’myFunc!’;}

• function myAdd($first, $second) {return $first+$second;

}• function mySub($first, $second=42) {

return $first-$second;}

• myFunc();echo myAdd(5, 18);echo mySub(42, 0); echo mySub(84);

• $f = ’myFunc’;$f(); // call myFunc(); NEVER EVER

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Variable scopeEvery variable is local!

$a = "Hello World";function hello(){

$a = "Hello Reader";$b = "How are you";

}hello();echo $a; // „Hello World”echo $b; // Warning: undefined variable $b

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Variable scope$a = "Hello"; $b = "World";function hello(){

global $a, $b;echo "{$a} {$b}";

}hello(); // „Hello World”

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$a = "Hello"; function hello(){

global $b;$b = "World";

}echo "{$a} {$b}“; // „Hello World”

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Exercise #1

Create a PHP script that generates two random integers (A [100 .. 1000], B [1 .. 20])!Echo them out, so that the user can see the numbers!

Then, create and call the functions for the followings:

• Calculate and return B! = 1*2*3*…*B• Calculate and return AB = A*A*A*…*A• Calculate and return Fib(B)

Fib(0)=0, Fib(1)=1, Fib(N)=Fib(N-1)+Fib(N-2) • Return (as a list in a string) every positive divisor of

the number A40OE NIK 2013

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Exercise #2

Generate 100 integers from the [150..200] interval.

Display the integers in a 10x10 table.

Emphasize the primes from the generated numbers.

Identify the maximum element, along with the number of occurrences of that element.

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PHP+SQL2.


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V 1.0 OE NIK 2013 1 PHP+SQL 2. PHP Introduction Control structures, operators Functions Practice ,