How to connect to 2 databases at the same time in PHP

Question

I am trying to connect to 2 databases on the same instance of MySQL from 1 PHP script.

At the moment the only way I've figured out is to connect to both databases with a different user for each.

I am using this in a migration script where I am grabbing data from the original database and inserting it into the new one, so I am looping through large lists of results.

Connecting to 1 database and then trying to initiate a second connection with the same user just changes the current database to the new one.

Any other ideas?

Answer 1

You'll need to pass a boolean true as the optional fourth argument to mysql_connect(). See PHP's mysql_connect() documentation for more info.

Answer 2

If your database user has access to both databases and they are on the same server, you can use one connection and just specify the database you want to work with before the table name. Example:

SELECT column
FROM database.table

Depending on what you need to do, you might be able to do an INSERT INTO and save a bunch of processing time.

INSERT INTO database1.table (column)
SELECT database2.table.column
FROM database2.table

Answer 3

Lucas is correct. I assume that both the databases are hosted on the same host.

Alternatively, you can create only 1 db connection and keep swapping the databases as required. Here is pseudo code.

$db_conn = connect_db(host, user, pwd);
mysql_select_db('existing_db', $db_conn);
 -- do selects and scrub data --
mysql_select_db('new_db', $db_conn);
-- insert the required data --

Answer 4

I would suggest using two connection handlers

   $old = mysql_connect('old.database.com', 'user', 'pass);
   mysql_select_db('old_db', $old);


   $new = mysql_connect('new.database.com','user','pass);
   mysql_select_db('new_db', $new)

   // run select query on $old
   // run matching insert query on $new

Answer 5

If it's an option, use PDO: you can have as many database connections open as you like.

Plus, assuming your executing the same queries over and over, you can use prepared statements.