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
A simple .php file with both HTML code and PHP code:
<!DOCTYPE html><html><body><h1>My first PHP page</h1><?phpecho "Hello World!";?></body></html>Note: PHP statements end with a semicolon (;).
PHP Case Sensitivity
In PHP, 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 equal and legal:
Example
ECHO is the same as echo:
<!DOCTYPE html><html><body><?phpECHO "Hello World!<br>";echo "Hello World!<br>";EcHo "Hello World!<br>";?></body></html>Note: However; all variable names are case-sensitive!
Look at 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
$COLOR is not same as $color:
<!DOCTYPE html><html><body><?php
$color = "red";echo "My car is " . $color . "<br>";echo "My house is " . $COLOR . "<br>";echo "My boat is " . $coLOR . "<br>";?></body></html>PHP Exercises
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