PHP获取表单textarea数据中的换行问题

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>PHP获取表单area数据中的换行问题</title>
</head>
<body>
<?php
$content=empty($_POST['content'])?null:trim($_POST['content']);
if(!empty($content))echo str_replace("r",'',nl2br($content));
echo "r".'<br/>----------分割线----------------------'."r";
if(!empty($content))echo str_replace("n",'nl',nl2br($content));
echo "n".'<br/>----------分割线----------------------'."n";
if(!empty($content))echo str_replace("r",'rl',str_replace("n",'nl',nl2br($content)));
echo "r".'<br/>----------分割线----------------------<br/>'."n";
echo 'hello'."n".'boys!';
echo 'hello'."r".'boys!';
?>
<form action="textareanl.php" method="post" enctype="multipart/form-data">
<textarea name="content" cols="20" rows="6"></textarea>
<br />
<input type="submit" value="提交" />
</form>
</body>
</html>

1.PHP函数nl2br()是在字符串中的每个新行(rn)之前插入HTML换行符:<br/>;

2.Windows下的换行是(rn);

3.在记事本中,r或n均有换行的功能;