怎样将下列正则中增加对特殊字符的支持？

[zairwolf]

<?
$post="[img]aaaa[/img]";
echo preg_replace("/\[img\](\r\n|\r|\n)*((http|https):\/\/([^;<>\*\(\)\"]+)|[a-z0-9\/\\\._\- ]+)\[\/img\]/isU","\\2",$post);

即可转换结果为aaaa，而我如果在aaaa中间加上一个问号，即$post="[img]aa?aa[/img]";就不能被转换。怎样增加对该字符的转换？

[caye]

echo preg_replace("/\[img\](\r\n|\r|\n)*((http|https):\/\/([^;<>\*\(\)\"]+)|[a-z0-9\/\\\._\- ?]+)\[\/img\]/isU","\\2",$post);