Fun fact. Wordpress is a well-known PHP based CMS so it's obviously possible to create a CMS in PHP with support for the features you want. As well as PHP, you are going to want a database to store content and other information, and a file system to store things like templates.
At this point, the advice you are going to get here is going to dry up. Designing a CMS isn't something we could answer in a QA forum. This requires analysis, requirements gathering, and design. If you have problems about a piece of code, please come back and ask; that's what this forum excels at - answering questions about concrete problems. I haven't looked at this video, but it might be of some use in getting started.
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