javascript 正则替换
var str = "<html><body><div>div内容</div><br>换行<br/><p>到底了</p></body></html>";
str = str.replace(/<(br[ ]?[/]?)>/g,"&_lt;$1&_gt;").replace(/</g,"<").replace(/>/g,">").replace(/&_lt;/g,"<").replace(/&_gt;/g,">");
document.write(str);
var str = "<html><body><div>div内容</div><br>换行<br/><p>到底了</p></body></html>";
str = str.replace(/<(br[ ]?[/]?)>/g,"&_lt;$1&_gt;").replace(/</g,"<").replace(/>/g,">").replace(/&_lt;/g,"<").replace(/&_gt;/g,">");
document.write(str);
$str = htmlspecialchars($str);
$str = str_replace("<br>", "<br>", $str);
$str='<html><body><div>div内容</div><br>换行<br/><p>到底了</p></body></html>';
echo preg_replace('/<(?!br)([^>]*)>/i','<$1>',$str);