php 判断图片文件的真实类型

/** *  * 检测文件的真实类型 *   * @param  string $srcPath 文件路径 *    * @return string $realType 文件真实类型 *     */$imgurl = 'http://pic.babytree.com/foto3/thumbs/2015/0506/51/8/357557aa334dd03923a408f_nb.jpg';echo file_type_detect($imgurl);function file_type_detect($srcPath){    $types = array(        6677    => 'bmp',        7173    => 'gif',        7368    => 'mp3',        13780   => 'png',        255216  => 'jpg',    );      $curl_obj = new cURL(false);    $binary = $curl_obj->get($srcPath);    //$binary = file_get_contents($srcPath);    $bytes = substr($binary, 0, 2);     $head = @unpack('C2char', $bytes);    $typeCode = intval($head['char1'].$head['char2']);    $realType = isset($types[$typeCode]) ? $types[$typeCode] : $typeCode;    return $realType;}