About Platform change

Question

Respected Experts
Please help me out to solve my query. I have join a company before few days but  on very start i  have to do work on php, but i have join as dot net developer. when i discussed with management they u need not not worry about platform everything is same only there are syntax difference and in future we have dot net project also they told (but i dont think so) as i am beginner and started my career just now please suggest me better decision