How to write a secure SELECT query which has a variable number of user-supplied values with mysqli?

Question

I would like some help to execute a foreach into my code.

I post multiple value into username : as username[0] = user1 , user2

but my foreach gi

Answer 1

Remove the '$value = $username_grab;' inside the foreach

i.e.

foreach ($username_grab as $value){
    // $value = $username_grab;   This does not belong

If that doesn't help, can you show the code this POSTs from and do a

print_r($username_grab)

just after you set it

Edit

 user1,user2 )
// $username = implode(",", $username_grab);                    // implode turns an array into a string using a delimiter
$usernames = explode(",", $username_grab[0]);                   // explode turns a string into an array by delimiter. The [0] index is for the post coming through as such
// $usernames should now look something like this. This is the array you will be working with
// Array ( [0] => user1, [1] => user2 )

foreach($usernames AS $value)
{
    $sql = "select * from linked_user where username = '" . mysqli_escape_string($value) . "' and company_name = '" . mysqli_escape_string($companyname) . "'"; // SQL injection is a threat. Seperate issue to look into   
    $res = mysqli_query($conn,$value);
    $cnt = 0;                                                   // Looking for multiple results. Counter for array
    while($row = mysqli_fetch_array($res))
    {
        $returnValue[$cnt]['username'] = $row['username'];      // Create a two dimensional array (multiple users. Each has their own index then
        $returnValue[$cnt]['user_scid'] = $row['user_scid'];    // Can replace the $cnt field with $row['userid'] (or whatever) if you have a primary key on the table i.e. $returnValue[$row['userid']]['username'] = $row['username'];
    }
    $cnt++;                                                     // Increase the counter for the next user
}

// $returnValue should now look something like this
// Array ( 
// [0] => Array (
//          ['username'] => 'user1', 
//          ['user_scid'] => 'whateverthedbsaysforuser1'),
// [1] => Array (
//          ['username'] => 'user2', 
//          ['user_scid'] => 'whateverthedbsaysforuser2'),
// )
echo json_encode($returnValue);
?>