defined

Function • Params and return types changed in PHP 8.0

Checks whether a constant with the given name exists.

PHP 5

PHP 7

Improved

PHP 8.1

PHP 8.2-8.3

PHP 8.4

PHP 8.5

PHP 8.6

`defined` Function synopsis

defined(string $constant_name): bool

Parameters

`$constant_name`

Typestring

The constant name.

Return value

Typebool

Returns true if the named constant given by $constant_name has been defined, false otherwise.

Changes to the `defined` Function

PHP 8.0

Return type added: bool
Parameter type added for parameter #1 ($constant_name): string

- defined($constant_name)
+ defined(string $constant_name): bool

`defined` Function Availability

PHP Version	Availability
PHP 8.6Upcoming Release	Yes
PHP 8.5Supported (Latest)	Yes
PHP 8.4Supported	Yes
PHP 8.3Security-Fixes Only	Yes
PHP 8.2Security-Fixes Only	Yes
PHP 8.1Unsupported	Yes
PHP 8.0Unsupported	Yes
PHP 7.4Unsupported	Yes
PHP 7.3Unsupported	Yes
PHP 7.2Unsupported	Yes
PHP 7.1Unsupported	Yes
PHP 7.0Unsupported	Yes
PHP 5.6Unsupported	Yes
PHP 5.5Unsupported	Yes
PHP 5.4Unsupported	Yes
PHP 5.3Unsupported	Yes