Chapter 02 php basic syntax

PHP Basic SyntaxPHP Basic SyntaxChapter 2

MOHAMAD RAHIMI MOHAMAD ROSMAN

IntroductionIntroduction

When you load a PHP page into a browser, it looks no different from an ordinary webpage. But before it reaches your browser, quite a lot goes on behind the scenes to generate the page’s dynamic content.

In most cases, this frenetic activity takes only a few microseconds, so you rarely notice any delay.

At first glance, PHP code can look quite intimidating, but once you understand the basics, you’ll discover that the structure is remarkably simple.


If you have worked with any other computer language, such as JavaScript, ActionScript, or ASP, you’ll find they have a lot in common.

Every PHP page must have the following:◦ The correct filename extension, usually .php◦ Opening and closing PHP tags surrounding each block of

PHP code◦ A typical PHP page will use some or all of the following

elements: Variables to act as placeholders for unknown or changing

values Arrays to hold multiple values Conditional statements to make decisions Loops to perform repetitive tasks Functions to perform preset tasks


Basic PHP SyntaxBasic PHP SyntaxMOHAMAD RAHIMI MOHAMAD ROSMAN

<?php

?>

<html><body><?phpecho "Hello World";?></body></html>

Below, is an example of a simple PHP script which sends the text "Hello World" to the browser:

Comments in PHPComments in PHP

PHP treats everything between the opening and closing PHP tags as statements to be executed, unless you tell it not to do so by marking a section of code as a comment.

The following three reasons explain why you may want to do this:◦ To insert a reminder of what the script does◦ To insert a placeholder for code to be added later◦ To disable a section of code temporarily


Comments in PHPComments in PHPMOHAMAD RAHIMI MOHAMAD ROSMAN

Single-line comments• The most common method of adding a single-line comment is to precede it with two forward slashes, like this:

Multiline commentsIf you want a comment to stretch over several lines, you can use the same style of comments as in Cascading Style Sheets (CSS). Anything between /* and */ is treated as a comment, no matter how many lines are used, like this:

Telling the server to process PHP

PHP is a server-side language. This means that the web server processes your PHP code and sends only the results—usually as XHTML—to the browser. Because all the action is on the server, you need to tell it that your pages contain PHP code.

This involves two simple steps, namely:◦ Give every page a PHP filename extension—the default is .php. Do not

use anything other than .php unless you are told to specifically by your hosting company.

◦ Enclose all PHP code within PHP tags. The opening tag is <?php and the closing tag is ?>. It’s a good idea to put the opening and closing tags on separate

lines for the sake of clarity.<?php// some PHP code?>

You may come across <? as an alternative short version of the opening tag.


Embedding PHP in a web page

PHP is an embedded language. This means that you can insert blocks of PHP code inside ordinary web pages. When somebody visits your site and requests a PHP page, the server sends it to the PHP engine, which reads the page from top to bottom looking for PHP tags.

XHTML passes through untouched, but whenever the PHP engine encounters a <?php tag, it starts processing your code and continues until it reaches the closing ?> tag.

If the PHP code produces any output, it’s inserted at that point. Then any remaining XHTML passes through until another <?php tag is encountered.


ExampleExample

Above figure shows a block of PHP code embedded in an ordinary web page


VariablesVariables

What is variables?◦ Variables are used for storing values, such as

numbers, strings or function results, so that they can be used many times in a script.

All variables in PHP start with a $ (dollar) sign symbol.

Variables may contain: ◦ Strings◦ Numbers◦ arrays


Naming VariablesNaming Variables

A variable name must start with a letter or an underscore "_"

A variable name can only contain alpha-numeric characters and underscores (a-Z, 0-9, and _ )

A variable name should not contain spaces. If a variable name should be more than one word, it should be separated with underscore ($my_string), or with capitalization ($myString)

Variables always begin with a dollar sign ($). The first character after the dollar sign cannot be a

number. No spaces or punctuation are allowed, except for the

underscore (_). Variable names are case-sensitive: $startYear and

$startyear are not the same.


• Dim Balance• $_balance• &_balance_due• $_balance_due• &_balance• $3_string• $35string• $Balance5• &_5Balance• $_Balance5• $_POST• $_GET


Which of the following variables is correct? Indicate T (true) or F (false)

Assigning values to variables

Variables get their values from a variety of sources, including the following:◦ User input through online forms◦ A database◦ An external source, such as a news feed or XML file

◦ The result of a calculation◦ Direct inclusion in the PHP code

Wherever the value comes from, it’s always assigned in the same way with an equal sign (=), like this:◦ $variable = value;


Assignment OperatorAssignment Operator

The variable goes on the left of the equal sign, and the value goes on the right.

Because it assigns a value, the equal sign is called the assignment operator.


Ending commands with a semicolon

PHP is written as a series of commands or statements. Each statement normally tells the PHP engine to perform a particular action, and it must always be followed by a semicolon, like this:


Missing SemicolonMissing Semicolon

You can omit the semicolon if there’s only one statement in the code block.

However, don’t do it. Get into the habit of always using a semicolon at the end of every PHP statement.

PHP is not like JavaScript or ActionScript. It won’t automatically assume there should be a semicolon at the end of a line if you omit it.

Caution: A missing semicolon will bring your page to a grinding halt.


Understanding when to use quotes

Numbers: No quotes◦ Eg: $StartYear=2007;

Text: Requires quotes◦ Eg: $Stu_Name=“Bill, Gray”;


Strings in PHPStrings in PHP

A string variable is used to store and manipulate a piece of text

The Concatenation OperatorThere is only one string operator in PHPThe concatenation operator (.) is used to

put two string values together.To concatenate two variables together,

use the dot (.) operator


ExampleExampleMOHAMAD RAHIMI MOHAMAD ROSMAN

<html><body>

<?php

$txt="Hello World";

echo $txt;

?>

</body></html>


<html><body>

<?php

$txt1="Hello World";$txt2="1234";$txt3="4321";echo $txt1 . " " . $txt3 . " " . $txt2 ;

?>

</body></html>

To concatenate two or more variables together, use the dot (.) operator:To concatenate two or more variables together, use the dot (.) operator:What is the output of the above script?What is the output of the above script?


<html><body>

<?php

$txt1=“1234";$txt2=“5678";$txt3=“9012";echo $txt2 . $txt3 . $txt2 ;

?>

</body></html>

To concatenate two or more variables together, use the dot (.) operator:To concatenate two or more variables together, use the dot (.) operator:

What is the output of the above script?What is the output of the above script?

Strlen() functionsStrlen() functions

Using the strlen() functionThe strlen() function is used to find the

length of a string

<?php echo strlen("Hello world!"); ?>

The output of the code above will be 12


H e l l o w o r l d !

1 2 3 4 5 6 7 8 9 10 11 12

strpos() functionstrpos() function

Using the strpos() function The strpos() function is used to search for a string or

character within a string. If a match is found in the string, this function will return

the position of the first match. If no match is found, it will return FALSE. <?php echo strpos("Hello world!","world"); ?>

*.start with 0


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0 1 2 3 4 5 6 7 8 9 10 11

PHP OperatorsPHP OperatorsChapter 2


Arimethic OperatorArimethic OperatorMOHAMAD RAHIMI MOHAMAD ROSMAN

Operator Description Example Result

+ Addition x=2x+2

4

- Subtraction x=25-x

3

* Multiplication x=4x*5

20

/ Division 15/55/2

32.5

% Modulus (division remainder) 5%210%810%2

120

++ Increment x=5x++

x=6

-- Decrement x=5x--

x=4

Assignment OperatorAssignment OperatorMOHAMAD RAHIMI MOHAMAD ROSMAN

Operator Example Is The Same As

= 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

Comparison OperatorComparison OperatorMOHAMAD RAHIMI MOHAMAD ROSMAN

Operator Description Example

== is equal to 5==8 returns false

!= is not equal 5!=8 returns true

> is greater than 5>8 returns false

< is less than 5<8 returns true

>= is greater than or equal to 5>=8 returns false

<= is less than or equal to 5<=8 returns true

Logical OperatorsLogical OperatorsMOHAMAD RAHIMI MOHAMAD ROSMAN

Operator Description Example

&& and x=6y=3 (x < 10 && y > 1) returns true

|| or x=6y=3 (x==5 || y==5) returns false

! not x=6y=3 !(x==y) returns true

SubstringSubstring

Finding the specific string in a wordssubstr(a,b,c);

◦ a: statement◦ b: starting point◦ c: Number of character

Example◦ Substr(“Fakulti IS”,8,2)◦ What’s the output for it?

* . The index start with 0.


F a k u l t i I S

0 1 2 3 4 5 6 7 8 9

ExerciseExercise

Provide answer for the following question.1.X=6, Y=10 Results

◦ x++ 7◦ x+=y 16◦ y-- 9◦ y%x 4◦ ((x--)+y)/ 5 3◦ (x*2)/12 1


ExerciseExercise

Indicate true or false1. x=5, y=8, z= “Hello” Results

◦ x==y False◦ x!=y True◦ x==5&&y==9 False◦ (x+3)>=y&& (y-3)>=x True◦ z!=“hello” True◦ $my_string!=$My_String True◦ z==“Hello”||z==“hello” True


Nurfatihah, Naimah, Aminah & Sairul has participated in the Mathematical competition. Out of 100 marks, Nurfatihah score 97, Naimah score 78, Aminah score 85, while Sairul score 82. Your task is:◦ Create 4 variable to store each candidate score◦ Display the mark for the following

Nurfatihah + Naimah – Aminah + Sairul Naimah – Sairul Sairul + Aminah

◦ Display average marks for all candidate


ExerciseExercise

1. x=“Nur” , y=“Fatihah”Write a PHP code using the above variable and answer the following questions. Length of x Length of y Length of x+y Combine the two variables together (xy) and

display it and then find the positon of i


ExerciseExercise

1. x=“Nazrul,Mohamad”1. First name = mohamad2. Last name = nazrul3. Change the order of the name, using the PHP

code. Display first name first, followed by last name.


ExerciseExercise

1. x=“Siti,Nurman,Fatimah”1. Variable x represents three (3) students of

IS110.2. Write a program to retrieve the name of the

last students, which is “Fatimah”.


ExerciseExercise

Create a script that request initial loan, interest, payback period, and display the data in the listbox alongside expected monthly payment.


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Chapter 02 php basic syntax