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 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:
<h1>My first PHP page</h1>
echo “Hello World!”;
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;
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:
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:
// This is a single-line comment
# This is also a single-line comment
This is a multiple-lines comment block
that spans over multiple
// You can also use comments to leave out parts of a code line
$x = 5 /* + 15 */ + 5;
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):
ECHO “Hello World!<br>”;
echo “Hello World!<br>”;
EcHo “Hello World!<br>”;
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):