I don't think we can talk about a standard "good" PHP developer. Being a good (PHP) developer is not just about technical skills.
I would say that a perfect PHP developer is aware of the PHP shortcomings and
also aware of PHP strengths. They made a conscious decision to use PHP for some projects (not necessarily for all projects). A perfect PHP developer is also very curious about what happens outside of their comfort zone: being curious about other frameworks, other CMSes, other languages, and other platforms.
A perfect PHP developer is one who can see value in learning different/new technologies. But at the same time, one who is able to choose the right technology depending on the task at hand. A perfect PHP developer knows when to use boring/proved technologies and when to test new/hyped technologies.