请问：怎么将sql查询结果生成多维数组

请教：如何将sql查询结果生成多维数组
我想实现的功能是这样的：
我传递一串数字供sql接收，数字的形式是菜品的ID值，类似“1,2,3，”，经过查询可以变成根据菜品分类而来的多维数组。


第一个问题，我如何将这个字符串分离开后循环利用sql查询并保存全部结果呢？

PHP code

<!--Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->$s=$ids;//接收到的ID字符串

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SQL code

<!--Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->$sqlslt_veginfo="select {$tb_veg}.veg_id,{$tb_veg}.vsort_id,{$tb_veg}.veg_name,{$tb_veg}.veg_preprice,{$tb_veg}.veg_favprice,{$tb_veg}.veg_picstr,{$tb_veg}.veg_ptfs,{$tb_veg}.veg_ts,{$tb_veg}.veg_fj from {$tb_veg} where {$tb_veg}.veg_id='{$s}'and {$tb_veg}.vdel_vfy='0'";$query_veginfo=$pdodb->query($sqlslt_veginfo);$array_veginfo=$query_veginfo->fetch(2);

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PHP code

<!--Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->$a=array(    "2" => Array        (            "1" => Array                (                    "id" => 728,                    "name" => "玉带香油莴笋",                    "preprice" => 68,                    "favprice" => 68,                    "pic" => jdcpic1342685874.jpg,                    "num" => 1,                    "ts" => 0,                    "fj" => ""                ),            "2" => Array                (                    "id" => 727,                    "name" => 新杭帮熏鱼,                    "preprice" => 38,                    "favprice" => 38,                    "pic" => jdcpic1342685755.jpg,                    "num" => 1,                    "ts" => 0,                    "fj" => ""                )        ),    "1" => Array        (            "1" => Array                (                    "id" => 749,                    "name" => 秘制日本二十头极品鲍鱼,                    "preprice" => 888,                    "favprice" => 888,                    "pic" => jdcpic1342688648.jpg,                    "num" => 5,                    "ts" => 0,                    "fj" => ""                ),            "2" => Array                (                    "id" => 748,                    "name" => 原汁慢煮焖煨中东干鲍鱼,                    "preprice" => 788,                    "favprice" => 788,                    "pic" => jdcpic1342688600.jpg,                    "num" => 1,                    "ts" => 0,                    "fj" => ""                ),            "3" => Array                (                    "id" => 747,                    "name" => 炝椒酱爆嫩鸡丁,                    "preprice" => 20,                    "favprice" => 20,                    "pic" => jdcpic1342688515.jpg,                    "num" => 1,                    "ts" => 0,                    "fj" => ""                )        ));

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";<br>print_r($array_veginfo);<div class="clear"></div>