Create thumbnails from external images?

I need some advice / tips for a function that can create thumbnails (2 different sizes) from an external image (url), then save the file name/path in mysql.

I´m working with a small portal for webcams, and I need to be able to download cam images (usually. Jpg) from users own websites, and then create thumbnails of them.

Preferably any function that does not require too much of my server (RAM, CPU and bandwidth).

 

Use the function file_get_contents() to fetch your photo and use phpthumb to create the thumbnails.