There is a wide range of quality in PHP code, and it depends mostly on the coder.
If your team uses simple php pages with inline code and a rats nest of includes like newbies did in 1999, it will be a disaster.
If they have progressed beyond that, you will have a range of experience from mediocre to excellent.
If your team has good coding conventions and practices and uses a modern framework (I use Yii on a current project and find it of high quality), they can write a solid maintainable app in PHP.
If your team uses simple php pages with inline code and a rats nest of includes like newbies did in 1999, it will be a disaster.
If they have progressed beyond that, you will have a range of experience from mediocre to excellent.
If your team has good coding conventions and practices and uses a modern framework (I use Yii on a current project and find it of high quality), they can write a solid maintainable app in PHP.