php替换的问题。一个小问题。求助

[xiangdeweiwangfengg]

就是这个小问题。我想把
<img src="attachments/month_0910/s2009102391151.gif" border="0" alt=""/>
替换为
<img src="http://www.ccav.com/attachments/month_0910/s2009102391151.gif" border="0" alt=""/>

于是我写了：

$rpstr = "<img src=\"attachments/month_";
$mystr = "<img src=\"http://www.ccav.com/attachments/month_";
$me = str_replace($rpstr,$mystr,@me);

提示：不能只替换attachments，有些特殊原因。必须要从src开始替换


但是不对，本人菜鸟，估计是字符转义的时候出了问题，所以发帖求助。
“<”,“/”,“=”空格 需要转义吗？
双引号“ " ”怎么转义呢？

[flyzz1]

字符串，空格！

[阿_布]

$str = "<img src='attachments/month_0910/s2009102391151.gif' border='0' alt=''/>";
echo preg_replace("/(src=')/","$1http:\/\/www.ccav.com\/",$str);

[阿_布]

$str = "<img src=\"attachments/month_0910/s2009102391151.gif\" border=\"0\" alt=\"\"/>";
echo preg_replace("/(src=\")/","$1http:\/\/www.ccav.com\/",$str);

[YHL27]

sf

[babysc1]

$str = "<img src=\"attachments/month_0910/s2009102391151.gif\" border=\"0\" alt=\"\"/>";
echo preg_replace("/(src=\")/","$1http:\/\/www.ccav.com\/",$str);