How much "unlearning" when I move to a PHP framework -

I'm aware of the benefits of using the PHP framework (though not the first hand, just SO read etc.) but I While using a "loose" framework, you control the new structure and you have to "unleash" many things and they have to learn again in a new way as if your New framework is required. Is it true, and which structure is the most flexible when it comes to this unmanageable aspect?

It depends only on how you have learned something.

It also depends on the special framework, adding some useful functions and suggestions, while others offer (or force) you use different types of development, Filestructures and Functions.

For example, you can still do pre_replace ('[A-Za-z]', $ user.name), still work, but is_alphabetical ($ user name) same) will talk.

You can still use the same task, but for some structures you need to recreate the structure of your program, while others use only the helpers, functions and database classes. To provide.

I have heard that this is the most well-known framework, when it comes to program structure, it is flexible, while there is more ideology.

This is not like Ruby on Rail or Dzegogo, where you will learn the total new language, you are still best to stick with the framework with good programming principles, rather than working with PHP.