PHP has a lot of quirks and inconsistencies in it that make many pieces of it confusing. Sometimes you have to look things up because they don't work the way you'd expect them to, and that slows you down. There's nothing that's really earth-shatteringly terrible about it, but people want things to be perfect. The truth is, no language is perfect, but perhaps PHP is less perfect than most others. (JavaScript has a ton of issues with it too, but for some reason people complain less about JS).