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
Comparing generators with Iterator objects
What References Are
Language Reference
PHP Manual
References Explained
Table of Contents
What References Are
What References Do
What References Are Not
Passing by Reference
Returning References
Unsetting References
Spotting References