省流！！✌

/**
 * 字符串压缩-加密
 */
function stringCompressEncode($string)
{
    $compressed = gzcompress($string, 9); //压缩级别为9
    return base64_encode($compressed);
}

/**
 * 字符串压缩-解密
 */
function stringCompressDecode($string)
{
    $compressed = base64_decode($string);
    $string = gzuncompress($compressed); 
    return $string;
}

详细！！

        $compressed = gzcompress($str, 9); //压缩级别为9

        $uncompressed = gzuncompress($compressed);

        echo $str, "\n";

        echo $uncompressed, "\n";

        echo base64_encode($compressed), "\n";

        echo bin2hex($compressed), "\n";

        echo urlencode($compressed), "\n";