Broken window theory, as it applies to code essentially says that sloppy code begets sloppy code. PHP itself has sloppy design, such as inconsistent argument order and naming conventions for built-in functions.

Most of the complaints I can think of about PHP that are objectively demonstrable are outdated. The language now has namespaces, closures and the like. Most of the complaints I have left have to do with the feel of the language, and some remaining cultural elements; it feels like a ghetto, even though it seems to have modern infrastructure now.