For one-dev sized projects (i.e. simple crud type apps) this may well work.
However I would be concerned about a couple of things if this were me and I was doing anything beyond the absolute most basic web app:
- long term maintenance. Doing something only you understand and only you can maintain (that job security you mention) is a bit of an unprofessional dick move IMO.
- if you need to get other people in to help, you now have to spend more time training then up on your custom system that they don't understand and keep an eye on them to make sure they are doing it right and not introducing security issues
- When your client wants to integrate with some common third party thing ("hey can we put Google maps in here?"/"we need to integrate with stripe payments") you'll need to reinvent the wheel from scratch to do it using your custom system rather than just use a well-supported off the shelf library.
- you'll need to stay 100% up to date on all security issues/approaches/classes of vulnerability to make sure your custom system is secure. Your audit was ok this time, but everytime you make a change to your custom library (e.g. to support Google maps or stripe) you're now going to need to go through the audits again to be sure you've not opened up any new security holes (and perhaps new ones you've not ever heard of because you are only working in this weird little custom system/thiefdom for the past 2 years)
- how to support the INEVITABLE requests for extra features that require something client-side that cannot be easily done with only PHP and static pages. It is not the 90s any more - the cat is out of the bag regarding interactivity ... the requests for client-side nicities that users are used to in other things WILL COME! Clients always want more! :-)
Still anyway I guess you don't need my good luck wishes as I am sure you are correct and that you really have out-thought and out-coded all of the well-supported and well-funded frameworks that have been built by many thousands of people and have been battle-tested in the field for years (e.g. Laravel, .net MVC, struts etc). Because otherwise if you hadn't totally out-smarted the entire industry, I'd be shitting myself and checking my professional liability insurance about now.