can i hook my PS3 up to my laptop?

Could i use an HDMI cable or something and hook my PS3 up to my laptop to use as a screen to play games on? Yes, my laptop does have an HDMI port

No, because the HDMI port found on your laptop is intended to transmit AV signals from the laptop to a monitor/TV.

Nope. The HDMI port on your laptop, and the one on your PS3, are both outputs.