"Works perfectly" != ready to be implemented in any project.
@xLaming Send me a PM if you need help to use composer.
Edit: I did a fast review of your code.
First, do you want to use PHP7 for this library?
Instead of cast each return of your functions, you can use https://www.php.net/manual/en/functions.returning-values.php#functions.returning-values.type-declaration
And returns are random, object/int/bool, can you use string? (return formated json)
About code replicate, you have 3 times is_epic, is_game... It would be better to create a private function.
After all these changes, you will be able to use composer.
Then if a developer wants to use your library, he can use "composer require xlaming/xatlib", and use it in his project "Use xlaming/xatlib" "$gifts = xatlib::userGifts(123456);"