How does PCP affect one's behavior?
While on PCP, your mood is very apt to change but will normally stray towards aggressiveness, sadness, or paranoia (1). People's self-images change, and they'll lose their ego, possible leading to depression and depersonalization, which makes the world seem further away.
How does PCP affect your relationships?
PCP has only negative effects on your relationships. The most basic problem with just about any drug is the arguments you have with friends or family about the use and abuse of said drug (1). Another problem is that PCP causes social withdrawal (1). When on PCP, you're paranoid of anyone and everyone and tend to stay away from them. You also have an inability to fulfill even the most basic of your responsibilities (1). If you live in your own home, you don't buy any food or pay bills or even go to work because your time is spent hallucinating and your money is spent on the drug. If you do live with your family or other friends, you're dead weight, taking up space and money and doing nothing but sitting around.