We present a systematic analysis for influence of phase φ on collisions of dissipative solitons, using the cubic-quintic complex Ginzburg—Landau equation in the absence of viscosity. Four generic outcomes are revealed upon the variation of gain/loss: merger of the two solitons into a single one; quasi-elastic interactions; creation of an extra soliton; and dissipation of the two solitons for in-phase. The velocities of the merger-soliton and the extra soliton can be effectively controlled by relative phase. The above features have potential applications in optical switching and logic gates based on interaction of optical solitons.