How to get Shipping Weight Total from the codeigniter cart class (its in the cart items array)

[eluser]dwhite7508[/eluser]
Hey guys,
I have a question about the cart class in codeigniter. This is probably more of an array question, but here it is...

I have my products in the codeigniter cart class and i've made a key and value for "weight". It works fine and when I do a print_r on $this->cart->contents() it shows the weight of each item just fine.

What i'm not sure of how to do (and i know this is probably simple) is loop through the cart contents and add up the total weight from each product array in the contents array.

Any ideas?