PHP Manual
Language Reference
Basic syntax
Types
Variables
Constants
Expressions
Operators
Control Structures
Functions
Classes and Objects
Namespaces
Errors
Exceptions
Generators
References Explained
Predefined Variables
Predefined Exceptions
Predefined Interfaces and Classes
Context options and parameters
Supported Protocols and Wrappers
Type Juggling
Basics
Language Reference
PHP Manual
Variables
Table of Contents
Basics
Predefined Variables
Variable scope
Variable variables
Variables From External Sources