<?php
function Topla($girdi){
	$cikti = array();
	foreach ($girdi as $satir) {
		if (array_key_exists($satir[1], $cikti)) {
			$cikti[$satir[1]] += $satir[2];
		}else{
			$cikti[$satir[1]] = $satir[2];
		}
	}
	return $cikti;
}

$kaynak = array(
	["C15", "BD1", "1"],
	["C15", "BD1", "1"],
	["C15", "BD1", "1"],
	["C16", "CD1", "1"]
);

print_r(Topla($kaynak));