PHP圖片縮小函數

刪除了原始圖片保留了操作後的圖片

  /**
 * 縮小圖片函數
 * @param string $fileName
 * @return void
 */
private function createSmallImg($fileName)
{
    list($width,$height,$type,$attr) = getimagesize($fileName);
    $imgOld=imagecreatefromjpeg($fileName);
    $imgObj=imagecreatetruecolor($width-100,$height-100);
    if(function_exists('imagecopyresampled'))
    {
    imagecopyresampled($imgObj,$imgOld,0,0,0,0,$width-100,$height-100,imagesx($imgOld),imagesy($imgOld));
    }
    else
    {
    imagecopyresized($imgObj,$imgOld,0,0,0,0,$width-100,$height-100,imagesx($imgOld),imagesy($imgOld));
    }
    imagedestroy($imgOld);
    unlink($fileName);
    imagejpeg($imgObj,$fileName,100);
    chmod($fileName,0777);
    imagedestroy($imgObj);