[php-src] Issue #11258: [Feature request] Add a path_join function

Issue: https://github.com/php/php-src/issues/11258 Author: shyim ### Description I really miss in PHP a function to join easily paths like the node's [path.join](https://nodejs.org/api/path.html#pathjoinpaths) or in other languages. I know it's really easy to implement in the user-land, but It would be nice to have this PHP as this is some base filesystem functionality like realpath, basename which should be included by default (in my opinion). ## Usage would be like: ```php path_join('/base', 'my', 'path'); // /base/my/path path_join('/base', 'my', 'path', 'test', '..'); // /base/my/path ``` ## Why not just string concatenation? When you concat just the paths you have to think about: - does the before path end with a /, you have to normalize all parts - for windows compatibility you have to use DIRECTORY_SEPERATOR