track_user_login.php

<?php
/**
 * Helper function to insert the user thats logged in
 * to the database
 */
function JwLanalytics_track_user_data_login($uid) {
  try {
    $timestamp = time();
    db_insert('users_logins_data')
      ->fields( array(
          'uid' => $uid,
          'timestamp' => $timestamp
      ))
      ->execute();
    JwLanalytics_expired_users_login_data(); // lets clean up the table after inserting stuff.a
  } catch(PDOException $e) {
    print $e; die;
  }
}

/**
 * Implements hook_user_login().
 */
function JwLanalytics_user_login(&$edit, $account) {
  JwLanalytics_track_user_data_login($account->uid);
}