Instead of asking questions you could start reading the source. Everything anyone can do with PocketMine is in there. "But there are many files! Where should I start?" The obvious answer to that would be either start.sh or start.cmd. "But that isn't a PHP file! Why do I need to read it?" When you read one of the start files you'll find the first clue "./src/pocketmine/PocketMine.php". It all starts with PocketMine.php. "Ok! Now what?" If you know PHP you know how functions and classes and objects work. Read PocketMine.php and try to understand what the code is doing. When you see a function or class you want to know more about then use the search function on http://php.net or https://github.com/pmmp/PocketMine-MP. We are not here to hold your hand or spoon feed you. You want to make a plugin so you also have to put some effort into it. Be specific when you ask questions. Provide code to show your effort. When you do all that and your plugin works you can be proud at yourself.
In this sense, every thread in the Resources forum should be sticky. We should have a StackOverflow documentation style resources forum to put the best threads on the top