Array Question

So, I have an array that looks like this rray(3) { [0]=> array(8) { ["line"]=> string(1) "1" ["ponbr"]=> string(5) "34474" ["emt"]=> string(3) "yes" ["qty"]=> string(1) "5" ["price"]=> string(2) "19" ["shipdate"]=> string(8) "11/06/07" ["tracking"]=> string(17) "11111111111111111" ["approved"]=> string(4) "true" } [1]=> array(8) { ["line"]=> string(1) "1" ["ponbr"]=> string(5) "TEST1" ["emt"]=> string(3) "yes" ["qty"]=> string(1) "5" ["price"]=> string(2) "19" ["shipdate"]=> string(8) "12/04/06" ["tracking"]=> string(9) "123123123" ["approved"]=> string(4) "true" } [2]=> array(8) { ["line"]=> string(1) "2" ["ponbr"]=> string(5) "TEST1" ["emt"]=> string(3) "yes" ["qty"]=> string(1) "5" ["price"]=> string(2) "12" ["shipdate"]=> string(8) "12/04/06" ["tracking"]=> string(12) "123123123123" ["approved"]=> string(4) "true" } } I want to see if the array["ponbr"] values matched then pick this array and construct another one with the matched arrays so I can get something like this [0]=> array(8) { ["line"]=> string(1) "1" ["ponbr"]=> string(5) "TEST1" ["emt"]=> string(3) "yes" ["qty"]=> string(1) "5" ["price"]=> string(2) "19" ["shipdate"]=> string(8) "12/04/06" ["tracking"]=> string(9) "123123123" ["approved"]=> string(4) "true" } [1]=> array(8) { ["line"]=> string(1) "2" ["ponbr"]=> string(5) "TEST1" ["emt"]=> string(3) "yes" ["qty"]=> string(1) "5" ["price"]=> string(2) "12" ["shipdate"]=> string(8) "12/04/06" ["tracking"]=> string(12) "123123123123" ["approved"]=> string(4) "true" } What is the best way to do this efficiently? Thanks for your input!