Despite its widespread use, PHP is generally looked upon poorly from a design point of view. The consistency of function names and function argument order, lazily and borderline non-functional implementation of object oriented programming, can only receive requests via POST methods, slow version adoption (the PHP you learn right now may not work on every webserver you'll work on), and a focus on "hacking things together" rather than "doing it right". These are all very common complaints when it comes to working with PHP. While not a bad language to learn, PHP is not at all a good language to learn first, as it will probably teach bad habits.

Many of the numerous samples, tutorials and code fragments out there contain serious security flaws or other bugs, like inproper input sanitisation. Sometimes the authors don't know any better, and sometimes they know but forget to mention that their code is not suited for productive systems. And even if they clearly state that their code needs additional checks and pieces not shown, people might skip over those last words, because it "works".