secondDb.php

<?php

public function Leaderboard() {
  $databaseConfig2 = array(
    'type' => 'MySQLDatabase',
    'server' => 'localhost', 
    'username' => 'username', 
    'password' => 'password', 
    'path' => '',
    'database' => 'silverstripe715'
  );
  DB::connect($databaseConfig2);	

  $leaders = Leader::get();
		
  global $databaseConfig;
  DB::connect($databaseConfig);
  
  return $leaders;
}