// connect.php
<?php
  $connection = mysqli_connect('localhost', 'root', 'root', 'loginapp');
   if(!$connection) {
       die("Database connection failed");
   }
 ?>


// showDb.php
<?php include 'connect.php' ?>
<?php
  function showAllData() {
      global $connection;
      $query = "SELECT * FROM users";
      $result = mysqli_query($connection, $query);
      if(!$result) {
        die("error");
      }

      while($row = mysqli_fetch_row($result)) {
        //$id = $row['id'];
        //echo "<option value='$id'>$id</option>";
        print_r($row);
      }

  }
 ?>