大神 急

<br />
$cart    = array(1=>array("id"=>1,"num"=>2),2=>array("id"=>2,"num"=>5));<br />
$newcart = array(1=>array("id"=>1,"num"=>4),3=>array("id"=>3,"num"=>4));<br />
foreach( $newcart as $k=>$v ){<br />
<br />
   if( $cart[$v['id']] ){<br />
         <br />
       $cart[$v['id']]['num'] += $v['num']; <br />
     <br />
   }<br />
   else{<br />
      <br />
      $cart = array_merge($cart,array($v));<br />
     <br />
   }<br />
<br />
}<br />

$cart = array(array("id"=>1,"num"=>2));<br />
 <br />
 $newcart = array(array("id"=>1,"num"=>4),array("id"=>2,"num"=>4));<br />
 foreach($cart as $v) $t[$v['id']]+=$v['num'];<br />
  <br />
 foreach($newcart as &$v){<br />
         $v['num']+=$t[$v['id']];<br />
 }<br />
$cart =$newcart; <br />
print_r($cart);