How can the padstring() function be modified to handle the ArgumentCountError and ensure proper functionality?

The padstring() function can be modified to handle the ArgumentCountError by checking the number of arguments passed to the function using the func_num_args() function. If the number of arguments is not equal to 3, an ArgumentCountError should be thrown. This ensures that the function is called with the correct number of arguments to ensure proper functionality.

function padstring($str, $length, $pad_char) {
    if (func_num_args() !== 3) {
        throw new ArgumentCountError("padstring() expects exactly 3 arguments");
    }
    
    $str_length = strlen($str);
    if ($str_length < $length) {
        $padding = $length - $str_length;
        $str = str_pad($str, $length, $pad_char, STR_PAD_RIGHT);
    }
    
    return $str;
}