According to Einstein's theory of photoelectric effect a single incident photon ejects a single electron. Therefore, when intensity increases, the number of incident photons increases, so number of ejected electrons increases, hence, photocurrent increases.
Now, maximum energy of electron $=\frac{1}{2} m v_{\max }^{2}$
and $\frac{1}{2} m v_{\max }^{2}=e V_{0}$, where $V_{0}$ is stopping potential.
Thus, the maximum kinetic energy of the electrons does not depend upon the intensity
of the incident rays, because the stopping potential is not affected by the increase of the
intensity of rays.