This is completely unnecessary and adds extra complexity for no good reason. Maybe it was used historically, but nowadays it is only used to identify players to send async-prepared batch packets to.
There are two alternative ways to do that:
1. use spl_object_hash() as the targets array in CompressBatchedTask
2. use ServerScheduler's object storage to retain references to the Player[] array.
I've opted for the second method.
Removing these identifiers allows great code simplification in removePlayer() and removes the need for those old stupid hacks.
This also includes a backwards-compatibility break by removing the $identifier parameter of Server->addPlayer().
All plugins will need to bump the API if they want to use this.
NOTE THAT THIS IS NOT THE FINAL API 2.0.0 AND THAT THERE WILL BE MORE CHANGES.
To start updating, you might also want to read https://secure.php.net/manual/en/migration70.php and specifically https://secure.php.net/manual/en/migration70.incompatible.php
To compile PHP7 with some of the required dependencies, use https://gist.github.com/shoghicp/166ab26ce5cc7a390f45
ONLY LINUX IS TESTED, DO NOT ASK FOR OTHER PLATFORMS!
----- THIS VERSION IS NOT SUPPORTED -----
This version WILL crash randomly in unexpected places due to PHP7, pthreads, PocketMine or cosmic rays.
Handle with care, and store under direct sunlight for the best performance.