(PHP 5 >= 5.2.0, PHP 7) Checks if variable of specified type exists

(PHP 5 >= 5.2.0, PHP 7) Gets external variables and optionally filters them

(PHP 5 >= 5.2.0, PHP 7) Filters a variable with a specified filter

(PHP 5 >= 5.2.0, PHP 7) Gets a specific external variable by name and optionally filters it

(PHP 5 >= 5.2.0, PHP 7) Returns the filter ID belonging to a named filter

(PHP 5 >= 5.2.0, PHP 7) Gets multiple variables and optionally filters them

(PHP 5 >= 5.2.0, PHP 7) Returns a list of all supported filters