Querying two databases with PDO - php

Question

I'm trying to change my queries from mysql to PDO because I need to query at the same time two different databases on different servers.
I've done these classes so far
class Db extends PDO {
public $db;
public function __construct($dbhost = 'host1', $dbname = 'db1', $dbuser = 'user1', $dbpass = 'user2', $dbtype = 'mysql') {
PDO::__construct($dbtype . ':host=' . $dbhost . ';dbname=' . $dbname, $dbuser, $dbpass);
}
function sql_query($sql) {
$result = PDO::query($sql);
return $result;
}
function sql_fetcharray($result) {
$rs = $result->fetch(PDO::FETCH_ASSOC);
return $rs;
}
function sql_numrows($result) {
$rs = $result->rowCount();
return $rs;
}
}
class Db2 extends Db {
public $db;
public function __construct($dbhost = 'host2', $dbname = 'db2', $dbuser = 'user2', $dbpass = 'pass2', $dbtype = 'mysql') {
PDO::__construct($dbtype . ':host=' . $dbhost . ';dbname=' . $dbname, $dbuser, $dbpass);
}
function sql_query($sql) {
parent::sql_query($sql);
$result = PDO::query($sql);
return $result;
}
function sql_fetcharray($result) {
$rs = $result->fetch(PDO::FETCH_ASSOC);
return $rs;
}
function sql_numrows($result) {
$rs = $result->rowCount();
return $rs;
}
}
and then
$db = new Db2;
$sql = "query";
$result = $db->sql_query($sql);
but the query affects only the second database.
Anyone can help?
Thanks a lot

Answer 1

you had to run your query twice against two databases. don't expect the inheritance to do that for you
$db = new Db2();
$sql = "query";
$result = $db->sql_query($sql);
$db1 = new Db();
$sql = "query";
$result1 = $db1->sql_query($sql);

Answer 2

I don't think you needed another child class, you can easily switch database using :
USE DATABASENAME
So for example you can do:
$db = new Db;
$sql = "query";
$result = $db->sql_query($sql);
$db->sql_query('USE DB2');
$sql2 = "query2";
$result2 = $db->sql_query($sql2);
or perhaps create a function to select db:
function select_db($db) {
$result = PDO::query('USE $db');
return $result;
}
then use it:
$db = new Db;
$sql = "query";
$result = $db->sql_query($sql);
$db->select_db('DB2');
$sql2 = "query2";
$result2 = $db->sql_query($sql2);