php合并二维数组相同的key

Question

有个二维数组：
$arr=array(
array('num'=>5,'period'=>3),
array('num'=>10,'period'=>3),
array('num'=>15,'period'=>9)
);
对period相同的值的数组，对num求和，怎么处理变成：
$arr=array(
array('num'=>15,'period'=>3),
array('num'=>15,'period'=>9)
);

Answer 1

把@mot的答案补完优雅一下：$arr=array(array('num'=>5,'period'=>3),array('num'=>10,'period'=>3),array('num'=>15,'period'=>9));$temp=array();foreach($arras$item){list($n,$p)=array_values($item);$temp[$p]=array_key_exists($p,$temp)?$temp[$p]+$n:$n;}$arr=array();foreach($tempas$p=>$n)$arr[]=array('num'=>$n,'period'=>$p);print_r($arr);

Answer 2

$tmp=array();foreach($arras$one){if($tmp[$one['period']])$tmp[$one['period']]=$tmp[$one['period']]+$one['num'];else$tmp[$one['period']]=$one['num'];}$arr=array();foreach($tmpas$key=>$value)$arr[]=array('num'=>$value,'period'=>$key);