I personally despise coding in PHP as much as anyone, but it has been used for a number of hugely successful projects, including Wikipedia and Facebook (that latter has even written a transpiler that converts PHP into C++). PHP is the bog standard on a LAMP stack so you know it will run on any environment, and there is a huge pool of programmers who know how to code it. Those are nontrivial reasons.
If you consider Wikipedia a good example of what PHP can do, we have irreconcilably different quality standards.
I think the technical debt of PHP is a huge reason why development of the software behind Wikipedia hasn't fixed any of the huge issues in the last 5 years.