$a = array(
0=>array('id'=>1,'name'=>'a','amount'=>1),
1=>array('id'=>2,'name'=>'b','amount'=>2),
2=>array('id'=>3,'name'=>'c','amount'=>3),
3=>array('id'=>1,'name'=>'a','amount'=>3)
);
$b = array();
foreach($a as $v) {
if(isset($b[$v['id']])) $b[$v['id']]['amount'] += $v['amount'];
else $b[$v['id']] = $v;
}
$b = array_values($b);
print_r($b);
结果就是：：
Array
(
[0] => Array
(
[id] => 1
[name] => a
[amount] => 4
)
[1] => Array
(
[id] => 2
[name] => b
[amount] => 2
)
[2] => Array
(
[id] => 3
[name] => c
[amount] => 3
)
)