Prove a relation about the Fourier transform

Question

I need to prove this relation $\int_{-\infty}^{+\infty}\phi(x)^2(m^2-\frac{d^2}{dx^2})dx=\int_{-\infty}^{+\infty}(m^2+k^2)\mid\hat{(\phi(k))^2}\mid\frac{dk}{2\pi}$ where $\hat\phi(k)$ is the Fourier transform of the function $\phi(x)$ and $\phi(x)$ is real function, when $\mid x\mid \rightarrow \infty$ function $\phi(x) \rightarrow 0$ I spent 5 hours on this already and couldn't come up with any solution