Is the epson xp 310 printer good for air print?

I need a printer to print some things from my iPhone 4. If I do get this printer what else do I need to buy for it? Or is there another printer that's better for air print?

Yes,310 printer is very good for printing some things from your iPhone 4 and you can easily do it, you may see following link:
http://www.mechcrew.com/services/printer-support/hp-printer-support.html

While the XP-310 is certainly a good printer, for not a significant amount more, you could the XP-410 which has a larger screen and more functionality. Here's a link to some other printers which also warrant consideration. There are two price brackets: under $100 and over $100

Epson wins for best price/feature comparison, best warranty and lowest cost of ink. You can't beat their warranty. If anything goes wrong, they will fedex a replacement and pick up the old one at their expense. You can get ink for under 50 cents a cartridge at www.ccs-digital.com. You pay under 2.50 for reusable cartridges and then get $2 back for the empties. Or you can buy refillables (which is what I'm using now) and refill yourself for pennies. Take a look at the workforce 3520, 3530 and 3540. They have received hundreds of rave reviews on Staples and Amazon from people who bought them. I saw the 3540 for 139 at Staples and Amazon and the 3530 was $119 at Walmart. If you want to save some money, look at the workforce 2540 or the XP400, decent printers but not quite as good.