Press your lips together to stop the air, then release. No vocal cord vibration.

Americans pronounce phd as pee-aych-DEE (/ˌpiˌeɪtʃˈdi/). Stress falls on the third syllable — keep everything else short and quick. You'll hear it in sentences like "She is working on a phd dissertation in theoretical physics".
Record yourself saying "phd" and play it back. The mic stays on your device — nothing's uploaded.
3 syllables, 6 sounds. Tap a syllable to jump to its row, then explore each sound's mouth shape and how it's made.
Start with your jaw slightly open and the front of your tongue forward and slightly up. Glide upward, your jaw closes a little more and your tongue arches higher toward the roof of the mouth.
Touch the front of your tongue to the roof of your mouth, then release into a 'sh' position. Flare your lips.

The textbook way isn't wrong — it's just not how anyone actually says it.
Stress falls on the third syllable, not the others. Stretch DEE — keep everything else short and quick.