Best approach to build a control panel for a website

I guess it depends on what the back end needs to do. I've done it both ways. Wordpress you get a lot for free, and if you can build a suitable back end for the client using something like Advanced Custom Fields plugin, it's kinda good for the client since it'll be easier for them to update their backend by hiring another wordpress developer if you're not available down the road for them.

But there is a point where you might have to twist, bend, and contort wordpress enough where it no longer becomes worth it. Just depends on what kind of custom data, and relational data the product needs. Than you have to decide between all the different languages and frameworks. Any of them would do it.

Be careful not to compare php to ruby on rails. You're comparing a language to a framework. Compare php to ruby, or laravel to rails, that way it's apples to apples.

If you're going to build one of these solutions, you should spend some time learning about all of them, and that information will lead you to make the best decision. There isn't a wrong answer here, there are just better answers.

For my first client website I used PHP and coded an admin panel myself. I do not recommend doing that, its just so much work. Using a framework like ruby on rails or laravel is nice because they have thought of a bunch of things you might miss, such as form tokens, form validation, password hashing, and a bunch of other stuff. You can code all of that yourself in PHP, but it probably wont be as good as what the laravel guys have done.

If you are new to PHP, you probably want to do a few simpler php projects before you get into laravel. A simpler option I hear is to use something like WordPress, which I dont know too much about.