title: Basic Syntax
A PHP script can be placed anywhere in the document.
A PHP script starts with
<?php and ends with
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
<html> <body> <h1>My first PHP page</h1> echo "Hello World!"; </body> </html>
The output of that would be :
My first PHP page Hello World!
Note: PHP statements end with a semicolon (;).
Comments in PHP
PHP supports several ways of commenting:
<html> <body> // 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>
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 are legal (and equal):
<html> <body> ECHO "Hello World!<br>"; echo "Hello World!<br>"; EcHo "Hello World!<br>"; </body> </html>
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):
<html> <body> "red"; echo "My car is " . $color . "<br>"; echo "My house is " . $COLOR . "<br>"; echo "My boat is " . $coLOR . "<br>"; $color = </body> </html>