如何让PHP在命令行中重新运行？

I'm completely at loss here and am about to wipe my hard drive clean and start from a fresh OS install. I've been trying for two days to create a new yii app in the terminal and have finally figured out that the terminal or command line can not even execute PHP all of a sudden. I had no problem in past creating an executing php from the command line, But now it's not working. When I type I'm completely at loss here and am about to wip