I wouldn't say it's unfounded but anecdotal. And I wouldn't necessarily call it "hate" either. PHP definitely isn't one of those technologies that you see often on job listings of major companies - sure they might use it for some things such as blogs but it's rarely part of the stack of their staple products. The question isn't whether they use it but to what extent and in what products.
On a quick search of PHP skills wanted on LinkedIn jobs I found the following large companies looking for it:
Apple,
Cloudflare,
Vimeo,
Box,
Slack,
Tesla,
Etsy,
Wayfair,
Shopify,
Facebook,
Etc
Clearly WordPress and Magento based businesses. Add in Facebook, Weebly/Square, and you realize that PHP probably drives more page views and powers more domain named sites than any other.
How are Vimeo and Slack Magento or Wordpress businesses? Etsy also most certainly does not primarily use those.
Facebook's codebase is overwhelmingly written in PHP.
If the F in FAANG doesn't qualify, then I don't know what does.
I know that a few years ago it was en vogue to say this but, hasn't HHVM diverged from off-the-shelf PHP? Facebook as a company has so many moving pieces written in so many different languages. Yes, the original codebase was a large PHP app. Last I heard, there was a decent amount of C++ and even some Haskell floating around.
Facebook's been using Hack for close to a decade now. Hack still strongly resembles PHP, but it's taken a different direction from PHP 7 and HHVM is no longer intending to be an alternative PHP runtime (https://hhvm.com/blog/2017/09/18/the-future-of-hhvm.html).