A Variable is an identifier used to store value. It can be changed or removed at any time. The variable name should start with a $ sign. The syntax is,
<?php
$variable_name = value;
?>
While declaring a variable we need not specify its data type. In PHP, the data type of its value is taken as the variable type. For example,
<?php
$message = "Welcome to PHPPOT";
$count = 5;
?>
In this example code snippet, the $message is a string variable whereas $count is int, based on the value.
PHP variable naming conventions
We need to follow the following rules while declaring variables in the PHP script.
- The variable name should be in alphanumerics.
- Special characters are not allowed except underscore(_).
- It should not be a pre-defined variable. For example, $this.
Types of variables
In PHP there is various type of variables. This categorization is based on the scope of the variable.
- Global variables – These variables have global scope and visibility to access from anywhere. For accessing them in a separate file, class or function we have to use the global keywords. For example global $global_variable_name.
- Local variables – The variables that are defined and used within some specific function or any other program block are called local variables.
- Superglobals – These are predefined global variables. For example, $_GET, $_SERVER and etc. It can be accessed from anywhere without the global keyword.
