<?php

$search = 'griffyn';
$truth = 'griffin';

$same = 0;
$different = strlen($truth);

$matching = '';

for($i = 0; $i < strlen($truth); $i++)
{
  if(isset($search[$i]) && $search[$i] == $truth[$i])
  {
    $same++;
    $different--;
    continue;
  }
  else
  {
    $matching = substr($truth, 0, $same);
    break;
  }
}

echo 'Different: ' . $different . '<br>';
echo 'Same: ' . $same . '<br>';
echo 'Matching Part: ' . $matching . '<br>';

?>