Given the skills you have already listed I am assuming that you want to be a web developer. If that is the case then PHP is a great skill to have as a web developer. That said you could look at C# &
ASP.net MVC - If you're coming from a SQL Server background. As a DBA I know PHP (from a past life) does it add anything to my paycheck each month? No not at all, did it help me get this job? No, because it is not relevant to my job as a DBA. Picking what to learn should be based on what you want from a career. If you're looking to become a web developer (again an assumption) make a portfolio website, create some sites that showcase your skills and use that to leverage work. Figure out your end goal and then work out what you need to learn to get you there - Do what you enjoy!