Phosphorus on reaction with $$NaOH$$  products $$P{H_3}$$  and $$Na{H_2}P{O_2}.$$   This reaction is an example of

Solution :
$$\mathop P\limits^0 + 3NaOH + 3{H_2}O \to $$     \[3Na{{H}_{2}}{{\overset{+1}{\mathop{PO}}\,}_{2}}+{{\overset{-3}{\mathop{PH}}\,}_{3}}\]
\[\begin{align} & \overset{0}{\mathop{P}}\,\to Na{{H}_{2}}{{\overset{+1}{\mathop{PO}}\,}_{2}}\text{(Oxidation)} \\ & \overset{0}{\mathop{P}}\,\to {{\overset{-3}{\mathop{PH}}\,}_{3}}\text{(Reduction)} \\ \end{align}\]
Simultaneous oxidation and reduction is disproportionation.