Honestly, my advice would be - don't feel intimidated. If you can code in PHP, you can understand React and it really can't be lost. It worth it to go out of your comfort zone sometime.
On the other hand, there is a whole momentum saying that using React and Angular for everything is over-engineering. I seriously thing PHP is on the descending side, but hey, there are still tons and tons of PHP engine out there and they will probably needs maintenance for the next few decades. Moreover, I think young developer will stop learning it as the web evolve, which will leave plenty of room for PHP developers.
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