Simple anagram checker in PHP

anagram.php

<?php

/*
 * 2016/12/12
 *
 * anagram.php
 * Simple anagram checker. (cAsE sEnsiTivE)
 *
 * Firman Gautama <firman.gautama@gmail.com>
 *
 */

$str1 = "abcabc123";
$str2 = "cbabca321";

$check = isAnagram($str1, $str2);
printf("String '%s' and '%s' is %s.\n", $str1, $str2, ($check ? "Anagram" : "Is Not Anagram"));

function isAnagram(&$str1, &$str2) {

  // check if both string have the same length.
  if (strlen($str1) !== strlen($str2)) {
    return false;
  }

  $t_s1 = Array();
  $t_s2 = Array();

  $len = strlen($str1);

  for ($i=0;$i<$len;$i++) {

    // map str1 character count
    if (empty($t_s1[$str1{$i}])) {
      $t_s1[$str1{$i}] = 1;
    }
    else {
      $t_s1[$str1{$i}]++;
    }

    // map str2 character count
    if (empty($t_s2[$str2{$i}])) {
      $t_s2[$str2{$i}] = 1;
    }
    else {
      $t_s2[$str2{$i}]++;
    }
  }

  // debug
  //print_r($t_s1);
  //print_r($t_s2);

  // if the character count is not same, that's mean the string is not anagram
  foreach ($t_s1 as $k => &$v) {
    if ($t_s1[$k] !== $t_s2[$k]) {
      return false;
    }
  }

  return true;
}