php - Multiple SQL inserts (number of inserts depending on number of user input) -

i have module on website allows admin add users group.

it build (with selectboxes), can select multiple users 1 group:

users:                       group: - user 1                     - group 1 - user 2                     - group 2 - user 3 - user 4 - user 5 

inside php, looks this:

$user_id = $_post["user_id"]; //this can array $group_id = $_post["group_id"];  if (count($user_id) == 1) {      $sql = "insert ignore users_groups (user_id, group_id) values ($user_id[0],$group_id)";  } elseif (count($user_id) == 2) {     $sql = "insert ignore users_groups (user_id, group_id) values ($user_id[0],$group_id), ($user_id[1],$group_id)";  } elseif (count($user_id) == 3) {     $sql = "insert ignore users_groups (user_id, group_id) values ($user_id[0],$group_id), ($user_id[1],$group_id), ($user_id[2],$group_id)";  } elseif (count($user_id) == 4) {     $sql = "insert ignore users_groups (user_id, group_id) values ($user_id[0],$group_id), ($user_id[1],$group_id), ($user_id[2],$group_id), ($user_id[3],$group_id)";  } elseif (count($user_id) == 5) {     $sql = "insert ignore users_groups (user_id, group_id) values ($user_id[0],$group_id), ($user_id[1],$group_id), ($user_id[2],$group_id), ($user_id[3],$group_id), ($user_id[4],$group_id)";  } else {     echo'error: many users selected';     exit; } 

how can in shorter code? maybe prepared statements because inputs users.

are looking this?

if(count($user_id)>5){     echo 'error: many users selected';     exit; } $sql = "insert ignore users_groups (user_id, group_id) values ($user_id[0],$group_id)"; ( $i = 1; $i < count($user_id); $i++) {     $sql .= ", ($user_id[$i],$group_id)" }