Fear of:

  Phobia

Pain  Algiophobia, Ponophobia, Odynophobia 
 or Odynephobia.
Paper  Papyrophobia.
Parasites  Parasitophobia.
Parents in law  Soceraphobia
Peanut butter sticking to the roof of the mouth  Arachibutyrophobia.
Pellagra  Pellagrophobia.
Penis, erect  Medorthophobia.
Penis, esp erect  Phallophobia.
Penis, erect: seeing, thinking about or having  Ithyphallophobia.
Penis, losing an erection  Medomalacuphobia.
People  Anthropophobia.
People in general or society  Sociophobia.
People, deformed or bearing a deformed child  Teratophobia.
Philosophy  Philsosphobia.
Phobias  Phobophobia.
Phobic prefering fearful situations  Counterphobia.
Pins and needles  Belonephobia.
Pins  Enetophobia.
Place: locked in an enclosed place  Cleithrophobia, Cleisiophobia, or Clithrophobia.
Place, being in a dark or gloomy  Lygophobia.
Places, certain  Topophobia.
Places, crowded public  Agoraphobia.
Places, open high  Aeroacrophobia.
Places or things, narrow  Stenophobia.
Plants  Botonophobia.
Pleasure, feeling  Hedonophobia.
Poetry  Metrophobia.
Pointed objects  Aichmophobia.
Poison  Iophobia.
Poisoned, being  Toxiphobia, Toxophobia, or Toxicophobia.
Poliomyelitis, contracting  Poliosophobia.
Politicians  Politicophobia.
Pope  Papaphobia.
Poverty  Peniaphobia.
Precipices  Cremnophobia.
Priests or sacred things  Hierophobia.
Progress  Prosophobia.
Property  Orthophobia.
Prostitutes or venereal disease  Cypridophobia, Cypriphobia,
 Cyprianophobia, or Cyprinophobia.
Punishment or flogging  Mastigophobia.
Punishment by a rod or other instrument, or of being severely criticized  Rhabdophobia.
Punishment  Poinephobia.
Puppets  Pupaphobia.
Purple, color  Porphyrophobia.
Rabies  Cynophobia, Hydrophobophobia,
 Hydrophobia, Kynophobia, or
 Lyssophobia.
Radiation or X-rays  Radiophobia.
Railroads or train travel  Siderodromophobia.
Rain  Ombrophobia or Pluviophobia.
Rape  Virginitiphobia.
Rat, great mole  Zemmiphobia.
Rectum or rectal diseases  Proctophobia or Rectophobia.
Red color or blushing  Erythrophobia, Erytophobia or
 Ereuthophobia.
Relatives  Syngenesophobia.
Religion or gods  Theophobia.
Religious ceremonies  Teleophobia.
Reptiles  Herpetophobia.
Responsibility or duty, neglecting  Paralipophobia.
Responsibility  Hypengyophobia or Hypegiaphobia.
Ridiculed, being  Catagelophobia or Katagelophobia.
Riding in a car  Amaxophobia.
Right side, things on the right side of the body  Dextrophobia.
Rivers  Potamphobia or Potamophobia.
Road travel or travel  Hodophobia.
Robbers or being robbed  Harpaxophobia.
Rooms, empty  Cenophobia or Centophobia.
Rooms  Koinoniphobia.
Ruin  Atephobia.
Running water  Potamophobia.
Russians  Russophobia.