I want to make a web app that can record the screen and the audio input to a computer.How can I use PHP to record the computer screen and the audio input to the computer.?
No. php runs on the server not on the client. You need to run client (i.e. in the browser) to capture its screen and audio and can then perhaps use php for processing and distribution. For client side tools you could start looking at html5 not sure how far they are with screen capturing at the moment.