php - 用PHP MySQL获取空白页

我得到的空白页面是下面的代码：

session_start();
include "config.php";
$af = $_GET['id'];
database_connect();
$query2 = "SELECT * FROM friends WHERE usr1 = '".$id."' AND usr2 = '".$af."'";
$result2 = mysql_query($query2) or die(mysql_error());
while ($row2 = mysql_fetch_assoc($result2)) {
if($row2['id']){
 echo "<script type='javascript'>alert('You are already friends with this person.');</script>";
 header('Location: profile.php?id="'.$af.'"');
}else{
    mysql_query("INSERT INTO friends (usr1, usr2)
            VALUES ('".$id."', '".$af."')") or die(mysql_error());
            echo "<script type='javascript'>alert('You two are friends now!');</script>";
        header('Location: profile.php?id="'.$af.'"');
};
};

这是config.php（尽管我在这里更改了变量）

$h = "localhost";
$u = "user";
$p = "pass";
$d = "datab";

$sql = 'SELECT id FROM craffyposts limit '.($page*$eachPage).','.$eachPage;

$sql_count = 'SELECT id FROM craffyposts';


function database_connect(){
    global $h, $d, $u, $p;

    $link = @mysql_connect("$h","$u","$p");
    $sql_error = mysql_error();

    if (!$link) {
        echo "Connection with the database couldn't be made.<br>";
        echo "$sql_error";
        exit;
    }

   if (!@mysql_select_db("$d")) {;
        echo "The database couldn't be selected.";
        exit;
    }
   return $link;
}

if($_SESSION['usrid']){
    database_connect();
    $query = mysql_query("SELECT * FROM craffyusers WHERE id='" .$_SESSION['usrid']. "' ") or die (mysql_error());
    while ($obj = mysql_fetch_object($query)) {
   $id = htmlspecialchars($obj->id);
   $username = htmlspecialchars($obj->username);
   $email = htmlspecialchars($obj->email);
   $realname = htmlspecialchars($obj->name);
   $srvrid = htmlspecialchars($obj->serverid);
   $propic = htmlspecialchars($obj->profilepic);
    };
};

这里有什么问题？

最佳答案

因为会有0或1个结果，所以可以删除while子句：

$row2 = mysql_fetch_assoc($result2);

if($row2 && $row2['id']){
 echo "<script type='javascript'>alert('You are already friends with this person.');</script>";
 header('Location: profile.php?id="'.$af.'"');
}else{
    mysql_query("INSERT INTO friends (usr1, usr2)
            VALUES ('".$id."', '".$af."')") or die(mysql_error());
            echo "<script type='javascript'>alert('You two are friends now!');</script>";
        header('Location: profile.php?id="'.$af.'"');
};