PHP replace help

function smiles ($str) {
  $simple_search = array(
    '/\:-D/is',
    '/\;-D/is',
    '/\:-\)\)\)/is',
    '/\:-\)\)/is',
    '/\:-\)/is',
    '/\:-P/is',
    '/\:-O/is',
    '/\:-\(/is',
  );
   
  $simple_replace = array(     
    "<img src='./img/smiles/emoticon_grin.png' alt='Grin' />",
    "<img src='./img/smiles/emoticon_wink.png' alt='Wink' />",
    "<img src='./img/smiles/emoticon_happy.png' alt='Happy' />",
    "<img src='./img/smiles/emoticon_happy.png' alt='Happy' />",
    "<img src='./img/smiles/emoticon_smile.png' alt='Smile' />",
    "<img src='./img/smiles/emoticon_tongue.png' alt='Tongue' />",
    "<img src='./img/smiles/emoticon_surprised.png' alt='Surprised' />",
    "<img src='./img/smiles/emoticon_unhappy.png' alt='Unhappy' />",
  );

  $str = preg_replace($simple_search, $simple_replace, $str);
  return $str;
}

echo smiles($text);