<?php
function persistence(int $num): int {
  $answer = 0;
  while ($num >= 9) {
    $parts = devideInt($num);
    $product = multiplyArrayElements($parts);
    $answer++;
    $num = $product;
    var_dump($num);
  }
  return $answer;
}

function devideInt(int $int): array{
	settype($int, "string");
	$letters = preg_split('//u', $int, null, PREG_SPLIT_NO_EMPTY);
	return $letters;
}

function multiplyArrayElements(array $array): int {
	$result = 1;
	
	foreach ($array as $number) {
		$result *= $number;
	}
	return $result;
}

$a = persistence(999);

echo $a;