You have two choices here with your enthusiastic philodendron. You can water it well and pull it out of the pot then transplant the entire thing into a larger container and it will continue to grow bigger. Or you can cut away the roots that overflow the pot and try potting the root segments into  6 inch pots of potting soil and they will most likely sprout to make new plants. Philodendron is a tough houseplant so cutting back some of the roots then replacing the plant into a container won't harm the mother plant. This process is called root pruning  and is often done to keep bonsai plants in a dwarf state, or houseplants small enough to stay indoors.  Keep growing, Marianne Binetti