if($format=='php')
{
  function highlight_code($code)
  {
    $code = trim($code);
    $code = substr($code, 0, 2) != "<?" ? $code = "<?php\n" . $code . "\n?>" : $code;
    return highlight_string($code ,true);
  }  
  $text=file_get_contents($file);
  echo highlight_code($text);
}