Variables play an important role in PHP, as they are places for holding values. In PHP, there is no need to declare variables. Variable can hold eight different data types: bloolean, integer, float, string, array, object, resource, or NULL.
PHP is a weakly typed language. This means that variable type varies depending on what is stored in the variable at the time. For example, if we have a variable $a, when $a = 0, $a is an integer type variable. If later we set $a = "New", then $a becomes a string type variable.
A variable name always starts with a $, followed by a letter or an underscore. The rest of the variable name can be a letter, a number or an underscore.
For example, $dog is a valid variable name, while @dog is not (@dog does not start with a $).
Variables in PHP are case-sensitive. For example, $Employee and $employee are two different variables.
In most cases, variables are local in scope. This means that variables declared within a function cannot be accessed outside of the function, and variables declared outside of a function cannot be access within the function.
To make a variable global, it must either be declared as global specifically, or it must be accessed using the $GLOBALS array.