Philodendron means "tree-loving," and most species in this genus are tree-climbing vines. Vines seek light by using trees to reach the top of what ecologists call the "canopy," where sunlight is available, unobscured by taller plants. Thus if your Philodendron is given free rein, you can expect it will grow across the room toward your halogen light.

Whether we consider a Philodendron growing indoors or one in the forest, a deeper question follows: How does this plant survive at a very low light level until it reaches the sunlight, or halogen lamp? To answer we need to understand how plants absorb light to make sugars and starchthat is, photosynthesize. Chlorophyll is the familiar pigment that gives plants their green color, but there is no free chlorophyll in the leafit is all bundled with specific proteins. The most abundant of these packages, the light-harvesting protein complex, absorbs light energy and passes it on to other complexes that begin the actual photosynthetic process. When a plant is short of light, it makes more of this light-harvesting complex; when it has plenty of light, it makes less. As a result, leaves at the ground level of a vine growing in the forest are a deeper green than leaves high up on the vine. Leaves are thus adapted to the light intensities they experience.

https://www.scientificamerican.com/article/how-can-philodendron-plan/