PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8
constant - Returns the value of a constant
Code Examples

constant( string$name ): mixed

Return the value of the constant indicated by name.

constant is useful if you need to retrieve the value of a constant, but do not know its name. I.e. it is stored in a variable or returned by a function.

This function works also with class constants.



The constant name.

Return Values

Returns the value of the constant.

Exceptions and Errors

An Error exception is thrown, if the constant is not defined. Prior to PHP 8.0.0, an E_WARNING level error was generated in that case.


Version Description
8.0.0 If the constant is not defined, constant now throws an Error exception; previously an E_WARNING was generated, and null was returned.

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