php 基礎有關問題二維數組求和

    php 基礎問題二維數組求和 !
    數組：
    $a = array(array("a"=>"aa","a1"=>1,"a2"=>1),array("a"=>"bb","a1"=>2,"a2"=>2),array("a"=>"cc","a1"=>3,"a2"=>3),
    array("a"=>"aa","a1"=>1,"a2"=>1),array("a"=>"bb","a1"=>5,"a2"=>5))
    第一個鍵值相同的元素 求和
    結果
    $r = array(array("a"=>"aa","a1"=>2,"a2"=>2),array("a"=>"bb","a1"=>7,"a2"=>7),array("a"=>"cc","a1"=>3,"a2"=>3));
    ------解決方案--------------------
    $a = array(
    array("a" => "aa", "a1" => 1, "a2" => 1),
    array("a" => "bb", "a1" => 2, "a2" => 2),
    array("a" => "cc", "a1" => 3, "a2" => 3),
    array("a" => "aa", "a1" => 1, "a2" => 1),
    array("a" => "bb", "a1" => 5, "a2" => 5),
    );
    $res = array();
    foreach($a as $r) {
    if(! isset($res[$r['a']])) $res[$r['a']] = $r;
    else {
    $res[$r['a']]['a1'] += $r['a1'];
    $res[$r['a']]['a2'] += $r['a2'];
    }
    }
    print_r(array_values($res));
    Array
    (
    [0] => Array
    (
    [a] => aa
    [a1] => 2
    [a2] => 2
    )
    [1] => Array
    (
    [a] => bb
    [a1] => 7
    [a2] => 7
    )
    [2] => Array
    (
    [a] => cc
    [a1] => 3
    [a2] => 3
    )
    )