Whew (verb)
To whistle with a shrill pipe, like a plover.
Phew (interjection)
Used to show relief, fatigue, or surprise.
“Phew, that took a long time to define!”
Phew (interjection)
Used to show disgust.
“Phew, it stinks in here!”
Wiktionary
Whew (interjection)
used to express surprise, relief, or a feeling of being very hot or tired
“whew—and I thought it was serious!”
Phew (interjection)
expressing a strong reaction of relief, or of disgust at a smell
“phew, what a year!”
Oxford Dictionary