Extract data from website via PHP

[nxnvn]

I am trying to create a simple alert app for some friends.Basically i want to be able to extract data "price" and "stock availability" from a webpage like the folowing two:

• http://www.sparkfun.com/commerce/product_info.php?products_id=5
• http://www.sparkfun.com/commerce/product_info.php?products_id=9279

I have made the alert via e-mail and sms part but now i want to be able to get the quantity and price out of the webpages (those 2 or any other ones) so that i can compare the price and quantity available and alert us to make an order if a product is between some thresholds.I have tried some regex (found on some tutorials, but i an way too n00b for this) but haven't managed to get this working, any good tips or examples?