PHP mysqli_change_user() Function

<?php
$con=mysqli_connect("localhost","my_user","my_password","my_db");

// Check connection
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }

// Reset all and select a new database
mysqli_change_user($con, "my_user" , "my_password" , "my_test");

mysqli_close($con);
?>