filter_var
Introduction
Variable and Type Related Extensions
PHP Manual

# Function Handling Functions

- Introduction
- Installing/Configuring
  - Installation
  - Runtime Configuration
  - Resource Types
- Predefined Constants
- Function handling Functions
  - call_user_func_array — Call a user function given with an array of parameters
  - call_user_func — Call a user function given by the first parameter
  - create_function — Create an anonymous (lambda-style) function
  - func_get_arg — Return an item from the argument list
  - func_get_args — Returns an array comprising a function's argument list
  - func_num_args — Returns the number of arguments passed to the function
  - function_exists — Return TRUE if the given function has been defined
  - get_defined_functions — Returns an array of all defined functions
  - register_shutdown_function — Register a function for execution on shutdown
  - register_tick_function — Register a function for execution on each tick
  - unregister_tick_function — De-register a function for execution on each tick

filter_var
Introduction
Variable and Type Related Extensions
PHP Manual