V.Shakya Software Developer & Consultant 
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The PHP script is executed on the server, and the plain HTML result is sent back to the browser.
Basic PHP Syntax
A PHP script can be placed anywhere in the document.
A PHP script starts with <?php and ends with ?>:
<?php
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// PHP code goes here
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?>
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The default file extension for PHP files is “.php”.
A PHP file normally contains HTML tags, and some PHP scripting code.
Below, we have an example of a simple PHP file, with a PHP script that uses a built-in PHP function “echo” to output the text “Hello World!” on a web page:
Example
<!DOCTYPE html> |
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<html> |
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<body> |
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<h1>My first PHP page</h1> |
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<?php
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echo "Hello World!"; |
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?>
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</body>
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</html>
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Note: PHP statements are terminated by semicolon (;). The closing tag of a block of PHP code also automatically implies a semicolon (so you do not have to have a semicolon terminating the last line of a PHP block).
Comments in PHP
A comment in PHP code is a line that is not read/executed as part of the program. Its only purpose is to be read by someone who is editing the code!
Comments are useful for:
To let others understand what you are doing – Comments let other programmers understand what you were doing in each step (if you work in a group)
To remind yourself what you did – Most programmers have experienced coming back to their own work a year or two later and having to re-figure out what they did. Comments can remind you of what you were thinking when you wrote the code
PHP supports three ways of commenting:
Example
<!DOCTYPE html> |
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<html> |
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<body> |
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<?php
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// This is a single line comment
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# This is also a single line comment
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/*
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This is a multiple lines comment block
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that spans over more than
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one line
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*/
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?>
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</body>
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</html>
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PHP Case Sensitivity
In PHP, all user-defined functions, classes, and keywords (e.g. if, else, while, echo, etc.) are NOT case-sensitive.
In the example below, all three echo statements below are legal (and equal):
Example
<!DOCTYPE html> |
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<html> |
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<body> |
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<?php
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ECHO "Hello World!<br>";
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echo "Hello World!<br>"; |
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EcHo "Hello World!<br>";
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?>
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</body>
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</html>
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However; in PHP, all variables are case-sensitive.
In the example below, only the first statement will display the value of the $color variable (this is because $color, $COLOR, and $coLOR are treated as three different variables):
Example
<!DOCTYPE html> |
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<html> |
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<body> |
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<?php
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$color="red"; |
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echo "My car is " . $color . "<br>"; |
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echo "My house is " . $COLOR . "<br>"; |
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echo "My boat is " . $coLOR . "<br>"; |
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?>
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</body>
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</html>
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