Anagram functions

anagram.php

<?php

// Using built in metod `count_chars`
function isAnagram(string $a, string $b): bool
{
    return count_chars(strtolower($a), 1) == count_chars(strtolower($b), 1);
}

// Using array_diff expected $a or $b consists from [a-z]
function isAnagram(string $a, string $b): bool
{
  $a = str_split(strtolower($a));
  $b = str_split(strtolower($b));

  if (count($a)!= count($b) ) {
      return false;
  }
  
  if (count(array_diff($a ,$b)) > 0 ) {
      return false;
  }
  
  return true;
}