For creating PHP packages several best practices has been established, like composer support (ofc) and putting the package on packagist, travis integration, directory organisation, tests, documentation and so on.
For further information i recommend these slides https://laravel-news.com/2015/08/hannes-van-de-vreken-package-development-slides/ which describe the situation very well.
And as we are all lazy, we like generators that scaffold a basic php package layout and luckily there are several out there.
They all differ a bit, so pick your favorite.
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