Variable is an identifier used to store value. It can be changed or removed by any time. Variable name should start with a $ sign. The syntax is,
$variable_name = value;
While declaring variable we need not to specify its data type. In PHP, the data type of its value is taken as the variable type. For example,
$message = "Welcome to PHPPOT";
$count = 5;
In this example code snippet, $message is string variable where as $count is int, based on the value.
PHP variable naming conventions
We need to follow the following rules while declaring variables in PHP script.
- Variable name should be in alphanumerics.
- Special characters are not allowed except underscore(_).
- It should not be pre-defined valiable. For example, $this.
Types of variables
In PHP there are various type of variables. This categorization is based on the the scope of the variable.
- Global variables – These variables has global scope and visibility to access from any where. For accessing them in separate file, class or function we have to use global keyword. 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 as local variable.
- Super globals – These are predefined global variables. For example, $_GET, $_SERVER and etc. It can be accessed from anywhere without global keyword.
This PHP code tutorial was published on May 17, 2013.
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