PHP is a programming language (that is, a formal grammar for specifying the operations a computer should perform), but also an implementation of an interpreter for that grammar. You're talking about the implementation, which is of fair quality (certainly better than, say, MRI Ruby) and very widely-deployed, a combination which many devs (brilliant or not) take advantage of.

People who say PHP is badly designed, however, aren't talking about the implementation; rather, they're strictly talking about the language itself—the syntax, the semantics, and the standard library. There is no advantage to the way PHP-the-language does things; it makes nonsensical choices (like the flat, disorganized, all-libraries-included function namespace, the inability to chain method calls in a single expression, the extreme amount of "weakly-typed" cruft surrounding the comparison operators, etc.) which derive no benefit.

It would be strictly beneficial to the programming ecosystem if PHP-the-language were treated as an object-code for other, better-designed languages to target, such that PHP-the-implementation could be used without needing to write in PHP.