If your speaking about putting a tile floor on the outside porch this can be done.
You need to have a very sturdy framing system first off. Most outside deck surfaces tend to be under framed and have a bit of movement as the result. If your sure your deck is not moving you need to install a uncoupling membrane such as Schluter Ditra system. http://www.schluter.com/6_1_ditra.aspx There are other membranes as this also but this in the one I am familiar with. The install is not much different then any other tile floor system. But you want to use the smallest grout lines and be sure to seal both the tile and grout very well and re-apply every year. As outside moisture can pop tiles and crack them easy. By using the sealant you lower the risk of moisture damage under the tile. The Ditra mat will seal off under the tile and reduce any movement that can damage the tile install when its not used. Some trims are available to finish off the edges of the porch where the tile ends.
Be sure to pick a tile that works outside well and that does not become slippery when it gets a bit of moisture on it.
If your installing over concrete...so much the better. As Woodbridge noted the "decoupling membrane" will provide for a better install. For outdoor tile I normally go with 3/16" grout lines and use sanded grout...sanded grout behaves better in hot cold environs