Checking for relation within a query

I am creating a friend system. I have a database table called 'friends'. The only time this table has records inserted into it is when a user attempts to add a friend or accept a friend request. Therefore friend relations are not default.

I am attempting to write a query which checks for friend relations, in order to properly set the correct button: Add Friend, Pending Request, Friends, Null.

My issue is I am only checking for a relation, therefore if I go to a user's page that I am not friends with, the query is not seeing the relationship and it causes my variables to be undefined.

Now to the code:

Please note that the parameters in the query's WHERE clause are $user_id and $profile_user.

$user_id is the user logged in.

$profile_user is the profile the logged in user is viewing.

So, if $user_id views his own profile or another user's profile (without relation, ie: sent a friend request), it throws error that the following variables are undefined:

$select_friend_1 = $friend_row['friend_one'];
$select_friend_2 = $friend_row['friend_two'];
$friend_status = $friend_row['status'];

In summary, how can I make my query work, so that a relation is not needed, but it still checks for the relation. I know the issue resides in my WHERE clause - just not sure what to change it to.

$okay = true;

//Checks 
if ( $okay ) {
    $friend_sql = "
        SELECT *
        FROM friends
        WHERE friend_one = ?
        AND friend_two = ?
    ";
    $select_friend_stmt = $con->prepare($friend_sql);
    $select_friend_stmt->execute(array($user_id, $profile_user));
    $friend_rows = $select_friend_stmt->fetchAll(PDO::FETCH_ASSOC);
    foreach ($friend_rows as $friend_row) {
        $select_friend_1 = $friend_row['friend_one'];
        $select_friend_2 = $friend_row['friend_two'];
        $friend_status = $friend_row['status'];
        $friend_status_date = $friend_row['date'];
    }
}
else {
    echo "Friend Status not found.";
}
$friend_status_button = null;
if ($friend_status == 2) {
    $friend_status_button = "Approved";
}
else if ($friend_status == 1) {
        $friend_status_button = "Pending";
}
else if ($select_friend_1 == $select_friend_2) {
    $friend_status_button = null;
}
else {
    $friend_status_button = "Add Friend";
}