Measurement of hadronic cross section at KLOE/KLOE-2

The measurement of the $\sigma(e^+e^-\rightarrow \pi^+\pi^-)$ cross section allows to determine the pion form factor $| F_\pi |^2$ and the two pion contribution to the muon anomaly $a_\mu$. Such a measurement has been performed with the KLOE detector at $DA\Phi NE$, the Frascati $\phi$-factory.The preliminary results on the combination of the last analysis (KLOE12) with two previous published (KLOE08, KLOE10) will be presented in the following.