PHP: [CRITICAL] Unable to find the PocketMine-SPL library.[CRITICAL] Please use provided builds or clone the repository recursively.bin\php\php.exe: Exit 1
You're not supposed to download the ZIP from GitHub. PocketMine contains submodules, which won't be included when downloading the ZIP with that button from GitHub. This will lead to your error. To fix this, either download a pre-built .phar file from Poggit or clone the repository --recursive with Git.
I wonder if someone could make a webpage that clones it recursively and packs it into a .zip, so stupid people can run pmmp from source...