public static function _mime_types($ext = '')
    {
        $mimes = array(
            'xl' => 'application/excel',
            'hqx' => 'application/mac-binhex40',
            'cpt' => 'application/mac-compactpro',
            'bin' => 'application/macbinary',
            'doc' => 'application/msword',
            'word' => 'application/msword',
            'class' => 'application/octet-stream',
            'dll' => 'application/octet-stream',
            'dms' => 'application/octet-stream',
            'exe' => 'application/octet-stream',
            'lha' => 'application/octet-stream',
            'lzh' => 'application/octet-stream',
            'psd' => 'application/octet-stream',
            'sea' => 'application/octet-stream',
            'so' => 'application/octet-stream',
            'oda' => 'application/oda',
            'pdf' => 'application/pdf',
            'ai' => 'application/postscript',
            'eps' => 'application/postscript',
            'ps' => 'application/postscript',
            'smi' => 'application/smil',
            'smil' => 'application/smil',
            'mif' => 'application/vnd.mif',
            'xls' => 'application/vnd.ms-excel',
            'ppt' => 'application/vnd.ms-powerpoint',
            'wbxml' => 'application/vnd.wap.wbxml',
            'wmlc' => 'application/vnd.wap.wmlc',
            'dcr' => 'application/x-director',
            'dir' => 'application/x-director',
            'dxr' => 'application/x-director',
            'dvi' => 'application/x-dvi',
            'gtar' => 'application/x-gtar',
            'php3' => 'application/x-httpd-php',
            'php4' => 'application/x-httpd-php',
            'php' => 'application/x-httpd-php',
            'phtml' => 'application/x-httpd-php',
            'phps' => 'application/x-httpd-php-source',
            'js' => 'application/x-javascript',
            'swf' => 'application/x-shockwave-flash',
            'sit' => 'application/x-stuffit',
            'tar' => 'application/x-tar',
            'tgz' => 'application/x-tar',
            'xht' => 'application/xhtml+xml',
            'xhtml' => 'application/xhtml+xml',
            'zip' => 'application/zip',
            'mid' => 'audio/midi',
            'midi' => 'audio/midi',
            'mp2' => 'audio/mpeg',
            'mp3' => 'audio/mpeg',
            'mpga' => 'audio/mpeg',
            'aif' => 'audio/x-aiff',
            'aifc' => 'audio/x-aiff',
            'aiff' => 'audio/x-aiff',
            'ram' => 'audio/x-pn-realaudio',
            'rm' => 'audio/x-pn-realaudio',
            'rpm' => 'audio/x-pn-realaudio-plugin',
            'ra' => 'audio/x-realaudio',
            'wav' => 'audio/x-wav',
            'bmp' => 'image/bmp',
            'gif' => 'image/gif',
            'jpeg' => 'image/jpeg',
            'jpe' => 'image/jpeg',
            'jpg' => 'image/jpeg',
            'png' => 'image/png',
            'tiff' => 'image/tiff',
            'tif' => 'image/tiff',
            'eml' => 'message/rfc822',
            'css' => 'text/css',
            'html' => 'text/html',
            'htm' => 'text/html',
            'shtml' => 'text/html',
            'log' => 'text/plain',
            'text' => 'text/plain',
            'txt' => 'text/plain',
            'rtx' => 'text/richtext',
            'rtf' => 'text/rtf',
            'vcf' => 'text/vcard',
            'vcard' => 'text/vcard',
            'xml' => 'text/xml',
            'xsl' => 'text/xml',
            'mpeg' => 'video/mpeg',
            'mpe' => 'video/mpeg',
            'mpg' => 'video/mpeg',
            'mov' => 'video/quicktime',
            'qt' => 'video/quicktime',
            'rv' => 'video/vnd.rn-realvideo',
            'avi' => 'video/x-msvideo',
            'movie' => 'video/x-sgi-movie'
        );
        return (array_key_exists(strtolower($ext), $mimes) ? $mimes[strtolower($ext)]: 'application/octet-stream');
    }