title: New string from multiple strings with most common words
body: <p>I am trying to create a new string from multiple strings using the most common words between these strings. For example:</p>
  
  <pre><code>$string[0] = 'Apple iPhone 4S 16GB Locked to Orange';
  $string[1] = 'iPhone 4S 16GB boxed new';
  $string[2] = 'iPhone 4S 16GB unlocked brand new';
  $string[3] = 'Apple iPhone 16GB 4S Special Offer';
  $string[4] = 'Apple iPhone 4S Sim Free';
  
  ## The new string should be:
  
  $new_string = 'Apple iPhone 4S 16GB';
  </code></pre>
  
  <p>There could be hundreds of original strings, or just 2...</p>
  
  <p>I don't have a clue where to start with this, any help would be really appreciated.</p>