012+ Fatal error: Uncaught TypeError: Argument 2 passed to array_walk_recursive() must be callable, string given in %s/array_walk_recursive_error1.php:28
013+ Stack trace:
014+ #0 %s/array_walk_recursive_error1.php(28): array_walk_recursive(Array, 'non_existent')
012- Warning: array_walk_recursive() expects parameter 2 to be a valid callback, function 'non_existent' not found or invalid function name in %s on line %d
013- NULL
014- Done
015+ #1 {main}
016+ thrown in %s/array_walk_recursive_error1.php on line 28