Does adjunct teaching help a PhD application?
It depends significantly on the particular PhD program you are applying to.

Where I am, teaching experience would be considered a significant positive.  It's not our main reason for having a graduate program, but one reason we have a graduate program (and perhaps the only reason we are allowed by the university to have a graduate program) is to have cheap labor for teaching some of our lower division courses.  We certainly appreciate having better teachers rather than worse ones, and experience helps.  Also, such experience indicates that you are not delusional about the outcomes from our PhD program and are aware that most academics jobs (if you are so lucky to get one) require teaching, frequently lots of teaching, of at least acceptable quality.

On the other hand, at a top ranked program with high-powered research, it probably won't help so much, and some professors may even consider it a slight negative because it indicates you might be interested in devoting time to something that is not research (and there is probably corporate work that is more research-like than teaching as an adjunct.)