PHP 7 binding

[jumpinjackie]

Version 3.0.11 was recently released which added long-awaited support for PHP 7.

As it is imperative that we escape the pending EOL of PHP 5.6 which is in less than 2 years time, we need to explore a usable path where we can bundle in PHP 7 and a MapGuide API binding that works with this version.

Current checklist:

• [x] Get downcasting to work. For example: MgSiteConnection::CreateService returns a proxy of MgService instead of the appropriate derived class
• [x] Test APIs that deal with MgByteReader to verify our byte typemaps are working
• [x] Because we downgraded to PHP 7.1, check if the pre-build sed patch workaround is still required
• [x] Make sure we can throw MgException based exceptions
• [x] Make sure MgException based exceptions are being properly released
• [ ] We should be building for the NTS (non-thread-safe) profile not TS as the binding in its current form (which is built for thread-safe PHP) cannot be used if hosting PHP in IIS (it uses non-thread-safe PHP). We can also use non-thread-safe PHP in Apache via mod_fcgid, so from a practical standpoint it's simpler to just build for the NTS profile.
• [ ] Since we've monkey-patched a custom destructor for MgException-derived proxy classes, find a way to get SWIG to not generate all those delete functions that will never get called.
• [ ] Put all the generated PHP code under a OSGeo\MapGuide namespace
• [ ] Get it building (Linux)
• [ ] Make existing PHP test suite pass (Windows)
• [ ] Make existing PHP test suite pass (Linux)

[jumpinjackie]

Our first attempt to run the PHP test suite with our binding gives us this warning:

Warning: dl(): MapGuideApi: Unable to initialize module
Module compiled with build ID=API20170718,TS,VC14
PHP    compiled with build ID=API20170718,TS,VC15
These options need to match
 in D:\Workspace\mapguide-api-bindings\src\Test\Php\MapGuideApi.php on line 16

And then failing afterwards.

Which tells me we have to downgrade to PHP 7.1 (at least on windows), where the official release is compiled with the same compiler (VS2015)