Doctor of Philosophy 
Port Hueneme Division 
Per Hatch Per Day 
Port Huron and Detroit Railroad 
Power Hybrid Doubler 
Pulse Height Discriminators 
Doctor of Philosophy degree 
Doctor of Philosophy in Education 
Duncan Aviation 
IATA code for Harry Clever Field, New… 
Parallel Head Disk 
Parallel Hybrid Device 
Personal Health Data 
Phage Host Defective 
Phase History Data 
Philosophiae Doctor 
Philosophiæ Doctor 
Philosophical Doctor 
Phosducin 
Photoelectron Diffraction 
Physical Hydrology Division 
Piled Higher and Deeper 
Pioneer Floating Rate Trust 
plant homeo domain 
plant homeo domains 
Playa Hatin Degree 
pleckstrin homology domain 
Pocket Hard-disk 
Poor Helpless Drunk 
Port Huron and Detroit Railroad Compan…