How to define PHP variables?

In PHP, variables can be defined using the following syntax:

$variableName = value;

In this case, $variableName is the name of the variable, which can be a combination of letters, numbers, and underscores, but must start with a letter or underscore. The value is the value to be assigned to the variable, which can be a string, number, boolean, array, etc.

Here are some examples:

$name = "John";
$age = 25;
$isStudent = true;
$numbers = array(1, 2, 3, 4, 5);

Please note that PHP is a dynamically typed language, meaning it automatically determines the variable type based on the value assigned to it.