count_duplicates.php

/*
 * Write a function that will return the
 * count of distinct case-insensitive alphabetic
 * characters that occur more than once in the
 * given string. The given string can be
 * assumed to contain only uppercase and
 * lowercase alphabets.
 *
 * @Input: a string
 * @Output: the number of unique characters that appear more than once
 *
 * @Examples: duplicateCount("abcde") = 0 // No characters repeat
 *            duplicateCount("aabbcdeB") = 2 // 'a' and 'b' repeat
 */
echo duplicateCount("aabbcdeB");
function duplicateCount($text) {
   
    $text = strtolower($text);
    $duplicate = 0;
    $checked = array();
   
    for ($i=0; $i < strlen($text) ; $i++)
    {
      for ($j = $i+1; $j<strlen($text) ; $j++)
      {
          if ( $text[$i] == $text[$j] && !in_array($text[$i],$checked) )
          {
            $checked[] = $text[$i];
            $duplicate++;
          }
      }

    }
    return $duplicate;
}