PHP Database connection practice

Question

I have a script that connects to multiple databases (Oracle, MySQL and MSSQL), each database connection might not be used each time the script runs but all could be used in

Answer 1

The best performance/practice rule is simple: do connect to one database only.

As for the connects - try to implement some database access class. Which can connect automatically on demand.

Answer 2

Use a lazy connection wrapper class:

class Connection
{
    private $pdo;
    private $dsn;

    public __construct($dsn)
    {
        $this->dsn = $dsn;
    }

    public query($sql)
    {
        //the connection will get established here if it hasn't been already
        if (is_null($this->pdo))
            $this->pdo = new PDO($this->dsn);

        //use pdo to do a query here

    }
}

I hope you're already using PDO. If not, you should be. PDO is database independent. If you did this using procedural functions, you'd have to create a new class for each database type.

Anyways, this is just a skeleton (you'd want to add a $params option in query(), for example), but you should be able to get the idea. The connection is only attempted when you call query(). Constructing the object does not make a connection.

As an aside, consider using Doctrine. It has lazy connections and makes life easier in general.