<?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;

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