defined() In Action¶
The defined() function checks if a constant is defined or not.
It is possible to check the constant with its name, and with its namespace.
Beware of quotes: most often, when checking for the constant’s value, the result is false.
On the other hand, it is not possible to check a constant with its aliased name: extra names, created with use are not validated.
To check for a class constant, it is possible to use a string, with the class name and the :: separator. Then, the visibility of the class constant is taken into account: it might be defined, but not accessible from that part of the code.
See Also¶
defined() in action [Try me]