Build a report based on php array

I have a 4 arrays, 2months ago past month and current month, all have the almost the same data, I need to group this arrays in order to build a "report"... this are basic arrays.. array([0]=>array(a,2,t,5), [1]=>array(a,2,t,5)... and so on, you get the picture, each key has date, names, zp, dob and a few others, what I need is to group them by date, right now shows, 2014-8-1 and this is repeated per record, I need to sum how many records from that date, how many records belong to the same ZP, how many records have the same DOB and so on... just like any other records, Like I said I already have the arrays all i need is to build them in groups so that I can use them to build html tables.. foreach ($a as $k=$v){ echo...} and so on... since I already have the arrays it should take long for someone with experience, and yes I need this urgently.. remember this are 6 arrays in total... 2 for 2 months ago, 2 for past month and 2 for current month, all you have to do is group them in different ways..