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(

            => 'bmp',

            => 'gif',

            => 'mp3',

           => 'png',

          => 'jpg',

    );

    $curl_obj = new cURL(false);

    $binary = $curl_obj->get($srcPath);

    //$binary = file_get_contents($srcPath);

    $bytes = substr($binary, , );

    $head = @unpack('C2char', $bytes);

    $typeCode = intval($head['char1'].$head['char2']);

    $realType = isset($types[$typeCode]) ? $types[$typeCode] : $typeCode;

    return $realType;

}