A variable is something that can be changed. It is used to store a value that may be changed. In php variable is starting with the symbol of $.

Declare a variable in php:

$variable_name = value;
Example: $web=5;
        Here $web is a Variable.

Note: Variables must be starts with $.

<?php
$a="good morning!";  //$variable_name = value;
$b=55;
?>

        Here $a and $b are variables. Values are 55 and ‘good morning’.

Naming Conventions of variables:

           Some Rules are set for declaring a name for variable. These rules are Naming Conventional rules.

	Variable name must start with a letter or an underscore "_".
	A variable name can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9, and _ ).
	A variable name should not contain spaces. If a variable name is more than one word, it should be separated with underscore ($my_string), or with capitalization ($myString).