A PHP script can be placed anywhere in the document.


A PHP script starts with <?php and ends with ?>:

Code:
<?php
// PHP code goes here
?>

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:

Code:
<html>
<body>

<h1>My first PHP page</h1>

<?php
echo "Hello World!";
?>

</body>
</html>
NB: 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

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:

Code:
<html>
<body>

<?php
// This is a single line comment

# This is also a single line comment

/*
This is a multiple lines comment block
that spans over more than
one line
*/
?>

</body>
</html>