In his latest post Evert Pot wonders if the current implementation of the "Callable" type in PHP is too loose when it comes to what it will accept as a valid callable resource.

PHP got support for closures in version 5.3, and in PHP 5.4 we got support for a callable typehint. [...] All these little changes make it feel more comfortable to apply functional programming concepts to PHP, but occasionally we need to drop back to using less aesthetically pleasing code.

In his examples of "less aesthetically pleasing code" he shows a few different methods that work that aren't the typical closure or object arguments (like passing in an array of object+method name). He also shows an interesting option where you can use a string with a static method call (ex: "MyClass::method") and it will still be accepted. He points out that for this to work correctly in all situations, the call_user_func method should be used, not just calling the input directly.

In this new post to his blog, Ed Finkler talks about some tests he worked up to discover if a function is available in PHP or not while working on the latest version of PHPSecInfo).

is_callable() will return TRUE even if a function has been disabled in php.ini with disabled_functions (which, in my mind, is contrary to what “is_callable” implies). function_exists() will return FALSE if the function is disabled in php.ini, but will return TRUE if the function is being blocked by safe_mode.

So, to help counter these issues, he checks first to see if the exec('id') option works - checking it work function_exists and the setting for safe_mode (disabled). If it doesn't pass, he moves on to the posix_* function and tests then with a function_exists.

In this new post to his blog, Ed Finkler talks about some tests he worked up to discover if a function is available in PHP or not while working on the latest version of PHPSecInfo).

is_callable() will return TRUE even if a function has been disabled in php.ini with disabled_functions (which, in my mind, is contrary to what “is_callable” implies). function_exists() will return FALSE if the function is disabled in php.ini, but will return TRUE if the function is being blocked by safe_mode.

So, to help counter these issues, he checks first to see if the exec('id') option works - checking it work function_exists and the setting for safe_mode (disabled). If it doesn't pass, he moves on to the posix_* function and tests then with a function_exists.