求过滤alt的正则表达式解决办法

$s =<<< TXT<br />
<P align=center><img alt=如果QQ我是你 src="/uploads/allimg/c100508/12I33243OF-12228.jpg" border=0><br />
   <img  alt=如果QQ我是你 src="/uploads/allimg/c100508/12I33243Y40-29608.jpg" border=0><br />
   <img  alt=如果QQ我是你 src="/uploads/allimg/c100508/12I33243c60-33252.jpg" border=0><br />
   <img  alt=如果QQ我是你 src="/uploads/allimg/c100508/12I332440Y0-410N.jpg" border=0><br />
   <img  alt=如果QQ我是你 src="/uploads/allimg/c100508/12I332441P-53227.jpg" border=0><BR><BR><br />
<img  alt=如果QQ我是你 src="/uploads/allimg/c100508/12I332442M0-62002.jpg" border=0><br />
  <img  alt=如果QQ我是你 src="/uploads/allimg/c100508/12I332443L0-N248.jpg" border=0><br />
  <img  alt=如果QQ我是你 src="/uploads/allimg/c100508/12I332444I0-X239.jpg" border=0><br />
   <img  alt=如果QQ我是你 src="/uploads/allimg/c100508/12I332445F-953E.jpg" border=0><br />
   <img  src="/uploads/allimg/c100508/12I33244C30-105E1.jpg" border=0 alt=如果QQ我是你></P><br />
TXT;<br />
echo preg_replace('/alt=([\'"]?).+?\1(\s<br><font color='#FF8000'>------解决方案--------------------</font><br>>)/is', '$2', $s);