php - 如何选择共同的 friend

Question

请我选择用户的共同好友，$my_id 是 $_SESSION['user'];而 $user_id 是选定的用户。这是代码:

    <?php

include 'connect.php';

include 'functions.php';

$my_frnds = mysqli_query{$con, "SELECT * FROM friends WHERE one='$my_id' OR two='$my_id'"};
while($my_friends = mysqli_fetch_array($my_frnds)){
    $one = $my_friends['one'];
    $two = $my_friends['two'];

    if($one == $my_id){
        $user == $two;
    } else
        $user == $one;
}

$user_frnds = mysqli_query{$con, "SELECT * FROM friends WHERE one='$user_id' OR two='$user_id'"};
while($user_friends = mysqli_fetch_array($user_frnds)){
    $user_one = $user_friends['one'];
    $user_two = $user_friends['two'];

    if($user_one == $my_id){
        $users == $user_two;
    } else
        $users == $user_one;
}

?>

假设我的 friend 是 (1, 2, 3, 4, 5, 6, 7)，用户 friend 是 (2, 4, 6, 7, 8, 9, 10)，所以共同的 friend 是 ( 2, 4, 6, 7) 我的问题是如何让共同的 friend 出去并回显他们的 ID？抱歉，我犯了一个错误，这是原始编码

Answer 1

如果一个是您的 ID，两个是 friend 的 ID:

select * from friends 
inner join (select * from friends where one = $user_id) as temp on temp.two = friends.two
where friends.one = $my_id