数据库访问错误，可能是一些php函数

我正在写剧本，但在某一点上被卡住了

但在文件下，它从用户那里获取用户id，并设置一个验证码并存储在数据库中，以便在访问时通知其他用户。代码是关于添加朋友、验证朋友并从列表中删除朋友。错误在于，当有人请求添加好友时，没有收到通知，而且另一方仍然可以将第一方添加为好友，但双方都没有收到任何效果。我想我无法了解实际的问题是什么……我已经检查了调用和访问功能，但无法找出问题出在哪里。数据库中的字段值如下-id/friend\u id/user\u id/verify\u code

这是密码-

@session_start();
if(empty($_SESSION["email"]) and empty($_SESSION["display_name"]) )
{
header("Location: ./login.php");
exit;
}

$user_id=get_user_data('user_id');

$id=$_GET[id];
//////////////////////////////////////////////////////////////////////////



//////////////////////////////////////////////////////////////////////////
if($_GET[f]=='verifyfriend' && $_GET[code]!='')
{ 
//confirm
$result=mysql_query("SELECT * FROM `friend` where `verify_code`='$_GET[code]' ");
if(mysql_num_rows($result)) // existing verify code.
{
//clear code
$row=mysql_fetch_assoc($result);
mysql_query("UPDATE `friend` SET `verify_code`='' WHERE                             `verify_code`               '$_GET[code]'");

    //add friend's friend
    mysql_query("INSERT INTO `friend` (`friend_id` ,`user_id` ) VALUES ('$row[user_id]', '$row[friend_id]') ");


    //update friend number: initiator
    $row2 = mysql_fetch_array(mysql_query("select * from `user` where user_id='$row[user_id]'"));
    $friends_num=$row2[friends_num]+1;
    $query="UPDATE `user` set friends_num='$friends_num' where user_id='$row[user_id]'";
    $result=mysql_query($query);
    //update friend number: friend
    $row3 = mysql_fetch_array(mysql_query("select * from `user` where user_id='$row[friend_id]'"));
    $friends_num=$row3[friends_num]+1;
    $query="UPDATE `user` set friends_num='$friends_num' where user_id='$row[friend_id]'";
    $result=mysql_query($query);


}



echo "<script>alert('".l('Friend added!')."'); location='/my/'</script>";




}


//////////////////////////////////////////////////////////////////////////
if($_GET[f]=='addfriend')
{
// 就是否已经是好友
$result=mysql_query("SELECT * FROM `friend` where user_id='$user_id' and friend_id='$id' and `verify_code`='' ");

if(mysql_num_rows($result)==0&&$user_id!=$id)
{
    $query="DELETE FROM `friend` where `user_id`='$user_id' and `friend_id`='$id' ";
    $result=mysql_query($query);

    $code=md5(rand());
    $query="insert into `friend` (`user_id`,`friend_id`, `verify_code`) values ('$user_id','$id', '".$code."')";
    $result=mysql_query($query);

    $url="http://"._DOMAIN_."/my/func.php?f=verifyfriend&code=".$code;
    mailcom($id,'addfriend',"$url");

    //////////end friend number////////
    echo "{'MSG':'1'}";
}
else
{
    echo "{'MSG':'0'}";
}
exit;
}
//////////////////////////////////////////////////////////////////////////
if($_GET[f]=='delfriend')
{
$result=mysql_query("delete from `friend` where user_id='$user_id' and friend_id='$id' limit 1");   
////////user 's  friend number //////////
    $row = mysql_fetch_array(mysql_query("select * from `user` where user_id='$user_id'"));
    $friends_num=$row[friends_num]-1;
    $query="UPDATE `user` set friends_num='$friends_num' where user_id='$user_id'";
    $result=mysql_query($query);
//////////end friend number////////
echo "<script>alert('".l('Friend deleted!')."');</script>"  ;

}

@session_start();
if(empty($_SESSION["email"]) && empty($_SESSION["display_name"]) )
{
header("Location: ./login.php");
exit;
}

$user_id=get_user_data('user_id');

$id=$_GET['id'];
//////////////////////////////////////////////////////////////////////////



//////////////////////////////////////////////////////////////////////////
if($_GET['f']=='verifyfriend' && $_GET['code']!='')
{ 
//confirm
$result=mysql_query("SELECT * FROM friend where verify_code='$_GET[code]' ");
if(mysql_num_rows($result)) // existing verify code.
{
//clear code
$row=mysql_fetch_assoc($result);
mysql_query("UPDATE friend SET verify_code='' WHERE verify_code = '$_GET[code]'");

    //add friend's friend
    mysql_query("INSERT INTO friend (friend_id, user_id) VALUES ('$row[user_id]', '$row[friend_id]') ");


    //update friend number: initiator
    $row2 = mysql_fetch_array(mysql_query("select * from user where user_id='$row[user_id]'"));
    $friends_num=$row2[friends_num]+1;
    $query="UPDATE user set friends_num='$friends_num' where user_id='$row[user_id]'";
    $result=mysql_query($query);
    //update friend number: friend
    $row3 = mysql_fetch_array(mysql_query("select * from user where user_id='$row[friend_id]'"));
    $friends_num=$row3[friends_num]++;
    $query="UPDATE user set friends_num='$friends_num' where user_id='$row[friend_id]'";
    $result=mysql_query($query);


}



echo "<script>alert('".l('Friend added!')."'); location='/my/'</script>";




}


//////////////////////////////////////////////////////////////////////////
if($_GET['f']=="addfriend")
{
// 就是否已经是好友
$result=mysql_query("SELECT * FROM friend where user_id='$user_id' and friend_id='$id' and verify_code='' ");

if(mysql_num_rows($result)==0 && $user_id!=$id)
{
    $query="DELETE FROM friend where user_id='$user_id' and friend_id='$id' ";
    $result=mysql_query($query);

    $code=md5(rand());
    $query="insert into friend (user_id, friend_id, verify_code) values ('$user_id','$id', '$code')";
    $result=mysql_query($query);

    $url="http://"._DOMAIN_."/my/func.php?f=verifyfriend&code=".$code;
    mailcom($id,'addfriend',"$url");

    //////////end friend number////////
    echo "{'MSG':'1'}";
}
else
{
    echo "{'MSG':'0'}";
}
exit;
}
//////////////////////////////////////////////////////////////////////////
if($_GET['f']=="delfriend")
{
$result=mysql_query("delete from friend` where user_id='$user_id' and friend_id='$id' limit 1");   
////////user 's  friend number //////////
    $row = mysql_fetch_array(mysql_query("select * from `user` where user_id='$user_id'"));
    $friends_num=$row[friends_num]-1;
    $query="UPDATE `user` set friends_num='$friends_num' where user_id='$user_id'";
    $result=mysql_query($query);
//////////end friend number////////
echo "<script>alert('".l('Friend deleted!')."');</script>"  ;

}