PMA\libraries\Util::getCompressionMimeType PHP Method

    public static function getCompressionMimeType($file)
    {
        $test = fread($file, 4);
        $len = strlen($test);
        fclose($file);
        if ($len >= 2 && $test[0] == chr(31) && $test[1] == chr(139)) {
            return 'application/gzip';
        }
        if ($len >= 3 && substr($test, 0, 3) == 'BZh') {
            return 'application/bzip2';
        }
        if ($len >= 4 && $test == "PK") {
            return 'application/zip';
        }
        return 'none';
    }

/**
 * Detects what compression the file uses
 *
 * @param string $filepath filename to check
 *
 * @return string MIME type of compression, none for none
 * @access public
 */
function PMA_detectCompression($filepath)
{
    $file = @fopen($filepath, 'rb');
    if (!$file) {
        return false;
    }
    return PMA\libraries\Util::getCompressionMimeType($file);
}