As an allegory Le Petit Prince by Antoine Saint-Exupery expresses lessons of friendship and altruism. Saint-Exupery once wrote, etre homme, etre responsable [to be man is to be responsible], and this expression of man's purpose is the philosophy of Saint-Exupery's The Little Prince. The relationship that the little prince has with his rose on the planet is pivotal to the novel as the prince learns that it is his responsibility to the rose, rather than his love for its beauty. In fact it is this responsiblity that drives him back to the planet and that gives his life meaning. The prince also learns that altruistic gestures are more rewarding than selfish ones.
In Saint-Exupery's allegory there are unnamed characters who symbolize certain phases of human life. For instance, the king represents authority, the businessman respresents greed, and the lamplighter respresents devotion to duty. The flower is a flirtatious woman, the serpent is death, the fox represents trickery. For instance, it is the fox who teaches the prince about the importance of one's responsibility to the loved one. He explains to the prince that by taming him, the prince has invested himself in the fox, thereby making the fox more special to the prince. Thus, what one gives to the loved one is more important than what one receives in return. Because of this lesson, the prince decides to return to his planet where his responsibility, the rose, needs him.
The links below will connect you to another question and another site on Saint-Exupery's novel which may be of help to you.