PHP : Extract user agent

gistfile1.php

<?php

$browser = "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_6; en-us) AppleWebKit/533.20.25 (KHTML, like Gecko) Version/5.0.4 Safari/533.20.27";

function extract_user_agent($agent)
{
  $found = array();
  $pattern  = "([^/[:space:]]*)" . "(/([^[:space:]]*))?";
  $pattern .= "([[:space:]]*\[[a-zA-Z][a-zA-Z]\])?" . "[[:space:]]*";
  $pattern .= "(\\((([^()]|(\\([^()]*\\)))*)\\))?" . "[[:space:]]*";

  while( strlen($agent) > 0 )
  {
    if ($l = preg_match($pattern, $agent, $a = array()))
    {
      array_push($found, array("product" => $a[1], "version" => $a[3], "comment" => $a[6]));
      $agent = substr($agent, $l);
    }
    else $agent = "";
  }

  return $found;
}

echo extract_user_agent($browser);

?>