Como sincronizar duas tabelas de bancos de dados MySQL diferentes na mesma máquina?

$mysql_host                 = DB_HOST;
$mysql_username             = DB_USER;
$mysql_password             = DB_PASSWORD;
$mysql_database1            = DATABASE1;
$mysql_database2            = DATABASE2;

$mysqli = new mysqli($mysql_host, $mysql_username, $mysql_password) or die( mysql_error());

/*  Begin Transaction   */
$mysqli->autocommit(FALSE); 


/*  Insert data from db1 to db2 */
$query  =  "    INSERT INTO $mysql_database1.table1";

$a  =   $mysqli->query($query); 

$query  =  "    INSERT INTO $mysql_database1.table2
            SELECT 
                *
            FROM $mysql_database2.table2
            WHERE NOT EXISTS(SELECT * from $mysql_database1.table2)     
";
$d  =   $mysqli->query($query); 


if ($a and $b) 
{
    $mysqli->commit();      
    echo "Data synched successfully.";
} else {        

    $mysqli->rollback();        
    echo "Data failed to synch.";
}