I know php ,mysql ,html and css ,but not getting opportunity to work on ,I tried for job also but not yet got selected ,what should I do

Before I comment on your skill set, I would like you to make sure that you applied for right job with right skills required to do the job and you know you have those (at-least 75% - 80%) skills as mentioned in the Job Description

In Market many companies are working on LAMP technologies (skills set you have mentioned) and so you need to search for right Job and then apply with confidence and you will get it soon