fourier - Phase information

I am quite new to MATLAB and I am currently trying to do some Fourier synthesis. In order to do the Fourier synthesis I need the phase information of the harmonics as a fraction of the period of the fundamental frequency. I am a bit lost on how to do this. Also I am trying to do a Fourier synthesis using the equation

$$y[i] = y[i-1] + p[j]\cdot \cos\left[2\pi f[j]\left(t- \dfrac{\gamma[j]}{f[1]}\right)\right]$$

Is this correct?