I'm the most terrific liar you ever saw in your life. It's awful. If I'm on my way to the store to buy a magazine, even, and somebody asks me where I'm going, I'm liable to say I'm going to the opera. It's terrible. ~J.D. Salinger, The Catcher in the Rye, Chapter 3

He is accusing everyone of being phony,but he is the most hypocritical person of all.He is pretending to have moral values and to be something he is not.He uses a word phony very often,even for people who are only his acquaintances.Holden is trying to achieve freedom trough his lies.It gives him wrong perception of the world and false feeling that he can be whatever he wants to be, without consequences and responsibilities.He doesn't have any direction in his life.

With his lies he gets false sense of a freedom.He gets pity from Mrs.Morrow by lying that he has brain tumor.Or lying that he is going to Opera instead of buying magazine he is acting like a snob and he is accusing others of snobby behavior.He admits he is a liar but that doesn't justify his actions.
Holden said he is the most terrific liar,but he is easily to be recognised as the one.He is very judgemental and if you judge people all the time ,you have to show more maturity in life,you have to be kind of role model.He is overprotective regarding Jane Gallagher ,he is fighting with Ward because he wants to be her guardian angel but at the same time he is using girls in the same way as Ward.
His attitude toward money is another example of him being pony. At the beginning he is calling his brother a prostitute because he makes good living writing screenplays in Hollywood.He admits leaving Pencey Prep that he has more then enough money but still ,he sells his skates to the other student.
And we see that his lies get more serious and will get him in trouble.The question is how long you can live that kind of life.One day he will not recognise himself,he will not know what is reality and what is his immaginery world.