Philip's dog is called ὁ Ἄργος. We call ours Rover, Lassie, Rex, King, Saphirina of Tenderbrooks etc, the Greeks called theirs Φύλαξ (the Greek word ὁ φύλαξ, τοῦ φύλακος meaning "guard, keeper", the one that φυλάττει τὸν οἶκόν τε καὶ τὰ πρόβατα (guards house and sheep, as it says in paragraph 1). Or Ἄργος.

The dog of Odysseus was also called  Ἄργος.
When Odysseus finally made it home from Troy, after 20 years' absence, his old dog, though nearly blind and deaf, recognized him immediately and then died in peace: master was back, safe and sound. Dogs in mythology and fairy tales obviously live much longer than ours do, in real life.
 
But why Ἄργος? ὁ Ζεύς, ὁ τῶν Ἑλλήνων θεός, was always having affairs, with goddesses, half-goddesses and beautiful mortal women. One of those was Io. To fool his wife Hera, he changed Io into a heifer (changing her back into her lovely human self when Hera wasn't around of course.) Unfortunately Hera was no fool and, when she saw her husband walking around with a heifer, a beautiful one at that, knew what was going on. So she became all coy and asked Zeus to make her a present, she'd seen such a lovely heifer, and would he please, please let his lady wife have her. Zeus couldn't refuse, and Hera handed Io over into the care of a herdsman called Argos Panoptes ( the All-Seeing One: πᾶν means "all" and 'optes' ? Think of "opticians" dealing with eyes for people to see better).
Argos had eyes all over his body so as to easily guard his flock against all evil.. Nor did those eyes ever all close at the same time; while some slept, the others kept watch.
Zeus was furious, he couldn't get anywhere near his lovely Io. So he sent Hermes to deal with the problem. Hermes managed to avoid being spotted and killed Argos.
It brought Zeus and Io no joy though, because Hera in her wrath sent gadflies to torment Io and never let her rest anywhere for long. And poor Argos? As a token of her gratitude, Hera took his eyes and put them on the tail of her favourite bird, the peacock, for all to see, forever. That's why that bird's tail is so beautiful, while its voice is horrendous. (I know, I've got a whole collection of them, peacocks I mean, not eyes.)
 
So to call a dog  Ἄργος is actually paying tribute to Hera's herdsman. If the dog is a good watch-dog, that is. I have my doubts about Philip's dog, though. Not the most obedient of canines.