PHP function missing argument error

Question

My validate function looks like that

function validate($data, $data2 = 0, $type)
{
...

Function call example

if ($result =          


        

Answer 1

Notice that starting with PHP 7.1 this will throw a PHP Fatal error, not just a warning:

PHP Fatal error:  Uncaught ArgumentCountError: Too few arguments to function validate(), 2 passed in /path/to/file.php on line X and exactly 3 expected

More info: http://php.net/manual/en/migration71.incompatible.php