A function that creates image thumbnails

/**
 * Create image thumbnail, return true if successful
 *
 * @param string $cat directory
 * @param string $oldname original image file name
 * @param string $newname new image file name
 * @param int $width abbreviation Thumbnail width
 * @param int $height Thumbnail height
 * @return
*/
function thumb($cat,$oldname,$newname,$width=160,$height=120){
  $srcFile = $cat. "/" .$oldname;
  $data = getimagesize($srcFile);
  $dscFile = $cat. "/". $newname;
   switch ($data[2]) {
    case 1:
    $im = imagecreatefromgif($srcFile);
    break;
    case 2:
    $im = imagecreatefromjpeg($srcFile);
    break;
    case 3:
    $im = imagecreatefrompng($srcFile);
    break;
   }
   $srcW=imagesx($im);
   $srcH=imagesy($im);
   if(($srcW/$width)>=($srcH/$height)){
    $temp_height=$height;
    $temp_width=$srcW/($srcH/$height);
    $src_X=abs(($width-$temp_width)/2);
    $src_Y=0;
   }
   else{
    $temp_width=$width;
    $temp_height=$srcH/($srcW/$width);
    $src_X=0;
    $src_Y=abs(($height-$temp_height)/2);
   }
   $temp_img=imagecreatetruecolor($temp_width,$temp_height);
   imagecopyresized($temp_img,$im,0,0,0,0,$temp_width,$temp_height,$srcW,$srcH);
   $ni=imagecreatetruecolor($width,$height);
   imagecopyresized($ni,$temp_img,0,0,$src_X,$src_Y,$width,$height,$width,$height);
   $cr = imagejpeg($ni,$dscFile);
   if ($cr){
    chmod($dscFile, 0777);
    return true;
   }
}
?>