db abstraction question

[Anon]

just wondering about peoples thoughts on createing db abstraction layers. Mainly I am trying to decide whether to use a general function like:

function connect_db($dbname){
[database connection to $dbname code goes here]
}

and then pass the db name for each connection i need to connect, or would I be better off creating functions like

function connect_db_users(){
[code to connect to db #1]
}

function connect_db_products(){
[code to connect to db #2]
}

etc... obviously the second method requires createing many more functions, but if I change the name of my database I dont neccesarily have to change any of my php code, except the function itself. i guess it bolis down to whether it is better to create flexible/general functions that can be reused more, or create specific functions that encapsolate situational information.

any thoughts?

[Anon]

I am slowly trying to implement a similar abstraction for my database connectivity. The model I am using is the following:

1. Create a file that contains variables for databases, ports, servers, tables, etc and include/require that at the top of each PHP file (dbinfo.inc)

$server = "my.db.server";
$db_users = "users_db";
$db_products = "products";
etc

2. Create the connectivity/query layer to take the server/db/table names that I need to use (as your first example does) and include/require that file (dblayer.inc)

function connect_db($dbname){
[do stuff here]
}

Now, if you change the name of your database, server, table names, etc all you have to do is change the information in the "dbinfo.inc" file without having to touch any code in the actual PHP files.
So far I have the first part working with the "dbinfo.inc" file, but I have yet to complete the db layer. I am also planning on writing in some error handling into the db layer so I can log errors to files and show "nice" error messages on the screen.

I'm sure opinions will vary on this and there have already been some good layers writen for several databases.

Hope that helps, and it might shorten your db layer a bit.

Tim Frank

[Anon]

That's exactly what I've been doing.

Plus, I autodetect in the connect code which machine/directory I'm in and connect to the appropriate databases for test or production.

You can also load balance in the connect section and / or detect failed backends and switch abstracted from the application.

I agree that you should keep the functions VERY generic, like connect_db, not connect_biz_rules_db and a dozen other connects.

$read_connect_id=connect_db($db_name,$server(s),$name,$pwd);
$result=query($read_connect_id,$query);
print build_table($result);
close_db($read_connect_id);

Or:

$write_connect_id=connect_db($dbname2,$server,$name,$pwd);
save_form_data($write_connect_id) or die("Couldn't save data to databas");

That's much easier to adjust and reuse.