PHP extensions

先查看 Bref 的 PHP 扩展文档和链接的 issue 评论，然后将当前的编译列表与提议的 gd、exif、mbstring、sodium 和 sqlite3 候选项进行比较。确认仓库用例所需的扩展集合，更新扩展配置，并验证 Lambda 构建是否能使用已达成一致的列表成功编译。

Currently, we compile with the following extensions enabled:

• Core
• bcmath
• ctype
• date
• fileinfo
• filter
• hash
• iconv
• json
• openssl
• pcre
• Phar
• posix
• Reflection
• session
• SPL
• standard
• tokenizer

Looking at https://bref.sh/docs/environment/php.html#extensions-installed-and-enabled and from scanning through use cases, the following could be interesting:

• gd, exif - image processing
• mbstring - prerequisite for exif anyways
• sodium - for crypto
• zlib - if we want to create ZIP files, HTTP compression - see https://github.com/xp-forge/lambda/issues/8#issuecomment-1184378957
• sqlite3 - for temporary data storage
• libxml, dom, xml, xmlreader, xmlwriter - for processing XML and HTML - see #11

The following extensions don't seem to make sense for an AWS lambda enviromment:

• pcntl - for parallelization, you would most probably just invoke other lambdas and/or use a message queue
• readline - this is for humans sitting in front of a terminal, not for the serverside
• curl, ftp, mysqli / mysqlnd - the XP Framework has it's own protocol implementations
• sockets - the standard socket library works just as well for (most - or almost all?) cases
• opcache - we leave our code running after compiling once, caching doesn't improve this any more
• SimpleXML - covered by XP Framework's XML APIs - used by AWS SDK, see https://github.com/xp-forge/lambda/issues/8#issuecomment-966497081