What is the name of a string words starting with ph?

There isn't one specific name for a string of words starting with "ph".

However, you could describe it as:

* A list of words beginning with "ph"

* A phrase starting with "ph" (if the words are connected in meaning)

* A sequence of words starting with "ph"

* A set of words with the initial digraph "ph"

Let me know if you have a specific list in mind, and I can help you further!