<?php
if($_POST['textarea']){
echo $_POST['textarea'];
}else{
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<form action="" method="post">
<textarea rows="30" cols="90" name="textarea">
<img src="http://bbs.php100.com/p_w_picpath/php100/logo.png" /> <br />
<img src=http://bbs.php100.com/p_w_picpath/php100/logo.png />
</textarea><br />
<input type="submit" value="提交" />
</form>
</body>
</html>
<?php
}
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title>Insert title here</title>
</head>
<body>
<form action="" method="post">
<textarea rows="30" cols="90" name="textarea">
<img src="http://bbs.php100.com/p_w_picpath/php100/logo.png" /> <br />
<img src="http://bbs.php100.com/p_w_picpath/php100/logo.png" />
</textarea><br />
<input type="submit" value="提交" />
</form>
</body>
</html>
没见你说的错误!