As a PHP developer you generally have two choices when it comes to developing web applications.
You can either use a framework or choose to write your application without the use of a framework.
I have mixed feeling about PHP frameworks, I think there is a time and a place for frameworks but they do not necessarily have to be used with every single project.
In my experience it is always a good idea to learn a framework such as
codeigniter or laravel, but only after you have mastered native or core PHP.
Develop a few web apps using core php before you dive into a framework.
Using a framework makes things easier but it can lead to relying too much on a framework.
I have had developers that use heavy frameworks even when a small task is requested.
For example I once tasked a developer to push data from a database to a URL, this should have been a simple script.
However this developer used a heavy framework to do this task, which took a lot longer that writing a
simple app in core PHP.
So you might be asking yourself when it is a good time to use a framework.
I believe you never really have to unless the application already uses a framework,
otherwise your app can run lean on core php. One could argue that frameworks
give your structure and make it so regardless of the developer as long as the web app
was written using the frameworks rules then any developer familiar with the framework should
know where files are located because framework standards make every project structure very similar.
To that I say as long as your organize and design your app properly there is no reason why
you cannot create an efficient file structure for your application and create documented
standards for future developers to reference if they are working on your app.
A lot of developers say learning a framework is a must and the next step after learning core synatx
although I do not think it is needed to create amazing application, I do see the value of learning a
framework as many applications are using frameworks and create a demand in the job market.