Melting point is the temperature at which a substance turns from solid to liquid (melts). Melting point is considered to be a physical property of a substance. Physical properties are measurable properties that allude to a substance's characteristics or state. Other examples of physical properties are density, solubility, atomic mass, and boiling point.
Below are the compounds listed within the question arranged from low to high melting points. All temperatures are in degrees Celcius.
PH3 (phosphine) = -132.8
NH3 (ammonia) = -77.73
H2O (water) = 0
SiO2 (silicon dioxide) = 1600
Melting point is in contrast to chemical properties, which describe the reactivity of a substance. For example, flammable and corrosive are words to describe chemical properties.
The chemteam.info describes chemical versus physical properties in more detail and gives additional examples of each.