function_exists() - find the file containing a given function in an object
string function_exists( string str, object ob );
Return the file name of the object that defines the function 'str' in object 'ob'. The returned value can be other than 'file_name(ob)' if the function is defined by an inherited object. 0 is returned if the function was not defined. Note that function_exists() does not check shadows.
call_other(3), call_out(3), functionp(3), valid_shadow(4)