/**     * 根据文件内容判断文件类型     * @param string $filename     * @return string     */    public function getFileType($filename){        $file = fopen($filename, "rb");        $bin = fread($file, 2); //只读2字节        fclose($file);        $strInfo = @unpack("c2chars", $bin);        $typeCode = intval($strInfo['chars1'] . $strInfo['chars2']);        $fileType = '';        switch ($typeCode) {            case 7790:                $fileType = 'exe';                break;            case 7784:                $fileType = 'midi';                break;            case 8297:                $fileType = 'rar';                break;            case 255216:                $fileType = 'jpg';                break;            case 7173:                $fileType = 'gif';                break;            case 6677:                $fileType = 'bmp';                break;            case 13780:                $fileType = 'png';                break;            default:                $fileType = 'unknown' . $typeCode;        }        if ($strInfo['chars1'] == '-1' && $strInfo['chars2'] == '-40') {            return 'jpg';        }        if ($strInfo['chars1'] == '-119' && $strInfo['chars2'] == '80') {            return 'png';        }        return $fileType;    }