With a PHP framework you
- Speed up custom web application development. ...
- Simplify web application maintenance. ...
- No need to write additional code. ...
- Work with databases more efficiently. ...
- Automate common web development tasks. ...
- Protect websites from targeted security attacks.
- Perform unit testing efficiently.
But
- It is not that secure due to its open-source, because the ASCII text file are often easily available.
- It is not suitable for giant content-based web applications.
- It has a weak type, which can cause incorrect data and knowledge to user.
If you know very good PHP, it is better to go for PHP, if you are in a harry with no ready PHP libs better go with the Framework.
For 1 - 2 programmers fast in work is Codeigniter
Best but a litthe difficult is Laravel, this is the king of PHP frameworks
