问个PHP数组合并的有关问题~请

问个PHP数组合并的问题~请高手指点

$arr1=array(<br />            "0"=>array(<br />                'id' => '2',<br />                'b' => 0,<br />                'num' => 4<br /><br />                ),<br /><br />            "1"=>array(<br />                'id' => '1',<br />                'b' => 0,<br />                'num' => 4 <br />                )<br />        );<br />        $arr2=array(<br />            "1"=>array(<br />                'id' => '3',<br />                'b' => 0,<br />                'num' => 4<br /><br />                ),<br /><br />            "2"=>array(<br />                'id' => '2',<br />                'b' => 0,<br />                'num' => 4 <br />                )<br />        );

想要合并这个两个数组，判断条件，id,b两个元素都相同的情况的NUM值相加。新数组键值重新排列0 1 2 3
求高手指点。谢谢。
------解决思路----------------------

$arr1=array(<br />            "0"=>array(<br />                'id' => '2',<br />                'b' => 0,<br />                'num' => 4<br /> <br />                ),<br /> <br />            "1"=>array(<br />                'id' => '1',<br />                'b' => 0,<br />                'num' => 4 <br />                )<br />        );<br /> $arr2=array(<br />            "1"=>array(<br />                'id' => '3',<br />                'b' => 0,<br />                'num' => 4<br /> <br />                ),<br /> <br />            "2"=>array(<br />                'id' => '2',<br />                'b' => 0,<br />                'num' => 4 <br />                )<br />        );<br />foreach($arr1 as $v) $res["$v[id]_$v[b]"] = $v;<br />foreach($arr2 as $v)<br />  if(isset($res["$v[id]_$v[b]"])) $res["$v[id]_$v[b]"]['num'] += $v['num'];<br />  else $res["$v[id]_$v[b]"] = $v;<br />print_r(array_values($res));

Array<br />(<br />    [0] => Array<br />        (<br />            [id] => 2<br />            [b] => 0<br />            [num] => 8<br />        )<br /><br />    [1] => Array<br />        (<br />            [id] => 1<br />            [b] => 0<br />            [num] => 4<br />        )<br /><br />    [2] => Array<br />        (<br />            [id] => 3<br />            [b] => 0<br />            [num] => 4<br />        )<br /><br />)<br /><br />