请高手帮忙写段正则代码，有点难

<a href="http://ygtc.tmall.com//search.htm?userId=&shopId=57299517&view_type=&order_type=&spm=0&search=y&keyword=%BA%A3%BB%EA%C9%C0&price1=&price2=" target="_blank"><img src="http://a.tbcdn.cn/kissy/1.0.0/build/imglazyload/spaceball.gif" src2="http://img01.taobaocdn.com/imgextra/i1/91615835/T2SFNZXdldXXXXXXXX_!!91615835.jpg_q75.jpg" data-ks-lazyload="http://img01.taobaocdn.com/imgextra/i1/91615835/T2SFNZXdldXXXXXXXX_!!91615835.jpg"></a>
   
</div>
<div style="width:1920px;padding:0;float:left;">

<a href="http://ygtc.tmall.com/search.htm?orderType=_hotsell&viewType=grid&baobei_type=&keyword=%BA%A3%BB%EA%C9%C0&price1=&price2=" target="_blank"><img src="http://a.tbcdn.cn/kissy/1.0.0/build/imglazyload/spaceball.gif" src2="http://img01.taobaocdn.com/imgextra/i1/91615835/T22K9BXohbXXXXXXXX_!!91615835.jpg_q75.jpg" data-ks-lazyload="http://img01.taobaocdn.com/imgextra/i1/91615835/T22K9BXohbXXXXXXXX_!!91615835.jpg"></a>
   
</div>
<div style="width:1920px;padding:0;float:left;">

<a href="http://ygtc.tmall.com/shop/view_shop.htm?spm=a1z10.3.0.324.DukoCY&search=y" target="_blank"><img src="http://a.tbcdn.cn/kissy/1.0.0/build/imglazyload/spaceball.gif" src2="http://img04.taobaocdn.com/imgextra/i4/91615835/T2Cmm8XixaXXXXXXXX_!!91615835.jpg_q75.jpg" data-ks-lazyload="http://img04.taobaocdn.com/imgextra/i4/91615835/T2Cmm8XixaXXXXXXXX_!!91615835.jpg"></a>
   
</div>
<div style="width:1920px;padding:0;float:left;">

<a href="http://ygtc.tmall.com/search.htm?spm=a1z10.1.w3.1.hqslaa&orderType=_hotsell&viewType=grid&baobei_type=&keyword=%C6%A4%D2%C2&price1=&price2=" target="_blank"><img src="http://a.tbcdn.cn/kissy/1.0.0/build/imglazyload/spaceball.gif" src2="http://img03.taobaocdn.com/imgextra/i3/91615835/T2YOeBXXdcXXXXXXXX_!!91615835.jpg_q75.jpg" data-ks-lazyload="http://img03.taobaocdn.com/imgextra/i3/91615835/T2YOeBXXdcXXXXXXXX_!!91615835.jpg"></a>
   

将上面的字符串中的src=""和src2=""和data-ks-lazyload=""中的""之间的内容提取出来，注意只要""之间的内容不包含""
[解决办法]
echo preg_replace_callback('/(<img src=")(.+?)(" src2=")(.+?)(" data-ks-lazyload=")(.+?)(">)/is','foo',$s);
function foo($src) {
return $src[1].md5($src[2]).$src[3].md5($src[4]).$src[5].md5($src[6]).$src[7];//这里只是简单写了下函数的处理方式，实际上处理方式不是这么简单，只是作为事例;
}