Checks if the interface has been defined
(PHP 5 >= 5.0.2)
Example 382. interface_exists() example
Code Examples / Notes » interface_exists
As far as I remember interface_exists() was added in 5.0.2 . In 5.0.0 and 5.0.1 class_exists() used to return TRUE when asked for a existing interface. Starting 5.0.2 class_exists() doesn't do that anymore.