Traversing an array usng for loops?

I have a query which returns a number of product details. there may be one or more rows for each product category.... for example: prod_ID feature_ID feature_cat_ID feature_value ..... 1 2 1 10 1 1 2 100 1 4 6 4 1 87 1 500 how do I process this array so that all my results for each feature-category are processed in their own for loops? ie : I want to go through the array for feature-category 1, and create a row in a HTML Table for each feature in category 1.. then move the category two, then three and so on. help! :)