Van Bryan at Classical Wisdom.
"As a general disclaimer, it is important to remember that Euthyphro was written by the philosopher Plato. While Socrates is used as a character in this dialogue, it is unknown if Socrates himself would have held such ideas. Although it is very possible that many of these thoughts were Socrates' it is also possible that the philosophy originated from Plato. However, because this is an early Platonic dialogue, it is largely considered to be an accurate reflection of the philosophy of Socrates."
See Plato, Dialogues, in Great Books of the Western World (first edition, 52 Vol., 1952) volume 7, (second edition, 60 Vol., 1990) volume 6.