新手提问：如何改变get的内容，页面没有改变

require 'Inc/function.php';

header("Expires:-1");

header("Cache-Control:no-cache");

header("Pragma:no-cache");



$user=$_POST["user"];

if (isset($user)){

	echo("0||");

	}

else{	

	$con = mysql_connect(DBHOST,DBUSER,DBPW);

	if (!$con)

	  {

	  die('数据库连接出错: ' . mysql_error());

	  }

	

	mysql_select_db(DBNAME, $con);

	

	$result = mysql_query("SELECT uid,password,salt FROM `pre_ucenter_members` where username='".checkstr(user)."'");

	mysql_close($con);

	

	$row=mysql_fetch_row($result);

	echo("$row[0]|$row[1]|$row[2]");

}

?>