usort
Introduction
Variable and Type Related Extensions
PHP Manual

# Class/Object Information

- Introduction
- Installing/Configuring
  - Requirements
  - Installation
  - Runtime Configuration
  - Resource Types
- Predefined Constants
- Examples
- Classes/Object Functions
  - __autoload — Attempt to load undefined class
  - call_user_method_array — Call a user method given with an array of parameters [deprecated]
  - call_user_method — Call a user method on an specific object [deprecated]
  - class_alias — Creates an alias for a class
  - class_exists — Checks if the class has been defined
  - get_called_class — the "Late Static Binding" class name
  - get_class_methods — Gets the class methods' names
  - get_class_vars — Get the default properties of the class
  - get_class — Returns the name of the class of an object
  - get_declared_classes — Returns an array with the name of the defined classes
  - get_declared_interfaces — Returns an array of all declared interfaces
  - get_declared_traits — Returns an array of all declared traits
  - get_object_vars — Gets the properties of the given object
  - get_parent_class — Retrieves the parent class name for object or class
  - interface_exists — Checks if the interface has been defined
  - is_a — Checks if the object is of this class or has this class as one of its parents
  - is_subclass_of — Checks if the object has this class as one of its parents
  - method_exists — Checks if the class method exists
  - property_exists — Checks if the object or class has a property
  - trait_exists — Checks if the trait exists

usort
Introduction
Variable and Type Related Extensions
PHP Manual