php二维数组处理

Question

$arr=array(
array('amount'=>100,'date'=>'2014-03-29'),
array('amount'=>120,'date'=>'2014-03-30'),
array('amount'=>200,'date'=>'2014-03-31')
);
怎么转化成以日期为准，amount为之前amount的和？
$arr=array(
array('amount'=>100,'date'=>'2014-03-29'),
array('amount'=>220,'date'=>'2014-03-30'),
array('amount'=>420,'date'=>'2014-03-31')
);

Answer 1

functionsd($a,$b){if($a['date']==$b['date'])return0;return$a['date']>$b['date']?1:-1;usort($arr,'sd');$amount=0;foreach($arras&$item){$amount+=$item['amount'];$item['amount']=$amount;}