$str='<div>代码库<img src="http://www.dmaku.com/images/logo.gif" /></div>';
$str= preg_replace('/<\s*img\s+[^>]*?src\s*=\s*(\'|\")(.*?)\\1[^>]*?\/?\s*>/i', '', $str);
echo $str;
$str='<div>代码库<img src="http://www.dmaku.com/images/logo.gif" /></div>';
$str= preg_replace('/<\s*img\s+[^>]*?src\s*=\s*(\'|\")(.*?)\\1[^>]*?\/?\s*>/i', '', $str);
echo $str;