Predefined Constants
List of Resource Types
List of Reserved Words
PHP Manual

## List of other reserved words

These words cannot be used to name a class, interface or a trait. These words are also prohibited from being used in namespaces. Some of the words are reserved to enable future PHP features without breaking backward compatibility.

Reserved words
int (as of PHP 7) | float (as of PHP 7) | bool (as of PHP 7) | string (as of PHP 7)
true (as of PHP 7) | false (as of PHP 7) | null (as of PHP 7) | resource (as of PHP 7)
object (as of PHP 7) | mixed (as of PHP 7) | numeric (as of PHP 7) |

Predefined Constants
List of Resource Types
List of Reserved Words
PHP Manual