Idiom is
a group of words in a fixed order that have a particular meaning that is different from the meanings of each word understood on its own.
Phrasal verb is
a verb in combination with a preposition or adverb or both that have a particular meaning that is different from the meanings of each word understood ot irs own.
Idioms can consist of pfrasal verbs but not the other way around.
Phrasal verbs do not have (well they sometimes do) fixed structure as idioms do (always).
Your question is very interesting by the way.
