Verify that the contents of a variable can be called as a function
is_callable ( mixed $var [, bool $syntax_only = FALSE [, string &$callable_name ]] ) : bool
The value to check
If set to TRUE the function only verifies that var might be a function or method. It will only reject simple variables that are not strings, or an array that does not have a valid structure to be used as a callback. The valid ones are supposed to have only 2 entries, the first of which is an object or a string, and the second a string.
Receives the "callable name".
Returns TRUE if var is callable, FALSE otherwise.
VAR | FUNCTION
VAR | METHOD
SYNTAX_ONLY | FUNCTION
SYNTAX_ONLY | METHOD
CALLABLE_NAME | FUNCTION
CALLABLE_NAME | METHOD