Actually, if I tell you in the simplest way then frameworks make your life easier and you don't need to build everything from scratch. You will get models to work with databases, Controllers to write business logic and views to show the frontend. Everything built feature will be aligned and remain separate from others in a nice way.
Well, it really depends on the size of your project. A homepage with no database and no more than 10 pages, a framework is going to be too much, mainly because frameworks always need a lot of configuration and customization in most cases, to fit specific needs. And in some situations, they could be a little slower than several pages included in a file (think about all the framework needs to load to use its features.).
Now, if you are planning a mid/big size site, with database interactions, web services, etc etc, you will need a framework to help you interact with different technologies and organize your code in a way that when things break, you'll have the ability to quickly detect and repair it. Also if you think about clients, they are always changing their mind about software, so if the client needs to modify or add a new feature you should not have to go through all your code and think about how do I plug this new feature in all this spaghetti.
@ginerjmAug 02.2018 — #What shahroznawaz is saying is that depending upon how much work you will be doing now and in the future, learning a framework can be either way too much learning/configuration or a god-send.
If you plan on ONE and only one appl you may as well not only learn PHP the old-fashioned way and get your project done. If you see this as the start of a long-term effort to create a site with multiple screens/appls then the investment in learning a framework can/will be worth it. The things that one can have already created for you via the framework will save you in the long run, assuming that you make smart choices with it and with your designs.
Personally I have been using native php for my website for several years now without benefit of any framework. Sure I have re-built the wheel several times but I have also created my own re-usable modules at the same time. I have no need to spend the time to pick up a framework as it is just me and I am under no deadlines to get things done quickly.
If you just creating a simple site for preview purpose then you don't need framework at all. Like I have created this https://github.com/forddyce/izeno-html for preview, without framework.
A lot of github project that can be installed independently as plugin also did not use framework.
However, if you are doing a complete app, you WILL need framework. For scale reasons, and when you are working with a team it makes things much simpler.