A 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
// 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:

 

Example

 

HelloWorld.php

 

<!DOCTYPE html>
<html>
<body>

<h1>My first PHP page</h1>

<?php
echo “Hello World!”;
?>

</body>
</html>

 

To deploy the example, open your XAMPP folder on your hard drive and enter the ‘htdocs’ folder.

 

 

Create a deployment folder e.g. HelloWorld. The full path for our example is;

C:\xampp\htdocs\HelloWorld\HelloWorld.php

 

 

Open the XAMPP Control Panel and Start the Apache service by clicking on the Start button associated with it. Click on the Admin Button to open the dashboard on your local browser.

 

 

 

To run the example type the URL:

http://localhost/HelloWorld/HelloWorld.php

 

 

Note: PHP statements end with a semicolon (;).

 

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 looking at the code.

 

Comments can be used to:

  • Let others understand what you are doing
  • Remind yourself of 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 several ways of commenting:

 

Example

 

<!DOCTYPE html>
<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 multiple
lines
*/

// You can also use comments to leave out parts of a code line
$x = 5 /* + 15 */ + 5;
echo $x;
?>

</body>
</html>

 

Output

 

PHP Case Sensitivity

 

In PHP, all keywords (e.g. if, else, while, echo, etc.), classes, functions, and user-defined functions are NOT case-sensitive.

In the example below, all three echo statements below are legal (and equal):

 

Example

 

<!DOCTYPE html>
<html>
<body>

<?php
ECHO “Hello World!<br>”;
echo “Hello World!<br>”;
EcHo “Hello World!<br>”;
?>

</body>
</html>

 

Output

 

 

However; all variable names 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):