<?php

...

$connection1 = mysqli_connect($host1, $user1, $pass1, $db1);
$connection2 = mysqli_connect($host2, $user2, $pass2, $db2);
$connection3 = mysqli_connect($host3, $user3, $pass3, $db3);

$repository1 = new MyRepository($connection1);
$repository2 = new MyRepository($connection2);
$repository3 = new MyRepository($connection3);