The question is not clear , let me clarify it:

    try{
$sql = '
SELECT UserID <==== (***********Used here for query ******)
FROM user
WHERE Rights != ?';
$stmt = $conn->prepare($sql);
$stmt->execute(array('admin'));
$result= $stmt->fetchAll();
}
catch(PDOException $e)
    {
    die ($e->getMessage().'<a href="add.php"> Back</a>'); 
    }

foreach ($result as $set)
{   
if ($set['UserID']==$_SESSION['username'])
$rights='edit';
else
{$rights=$_POST[$set['UserID']];}


if (($rights != 'default' || $set['UserID']==$_SESSION['username']) && $_POST['public']==0 )
{ 
$user=$set['UserID'];
try {
    $query="INSERT INTO user_list(UserID  <==== (***********Used here for insert ******),ListID,UserRights) VALUES ($user,$lastID,$rights)";
    $stmt = $conn->prepare($query);
    $stmt->execute();

}
catch(PDOException $e)
    {
    die ($e->getMessage().'<a href="add.php"> Back</a>'); 
    $conn->rollBack();
    }  
}
}

As you can see the UserID is a query result but it is also the column i need to insert, so when i insert into the table it will casued an error

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'UserA_ID' in 'field list' 

because the column is modify by my query result

from:

$query="INSERT INTO user_list(UserID,ListID,UserRights) VALUES ($user,$lastID,$rights)";

to:

$query="INSERT INTO user_list(query_result_id,ListID,UserRights) VALUES ($user,$lastID,$rights)";

How to fix it ?Thank you.