laser-phototransistor throughbeam detector

i am currently working on a project that requires an digital 1 output from a phototransistor when a laser beam falls on it and a zero when the beam is broken. however the problem is the setup needs to work indoors or outdoors. any ideas on how i can get around the ambient light difference to give a reliable signal??

Place the phototransistor inside a tube and point it at the laser. This has the effect of making it very directional.

Paint the inside of the tube black to absorb light.

You can also use an optical filter that only allows the color of the laser through it. That will block most ambient light.