What is the best method for getting a database connection/object into a function in PHP?

Question

A couple of the options are:

$connection = {my db connection/object};

function PassedIn($connection) { ... }

function PassedByReference(&$connection) {         


        

Answer 1

My advice is to avoid global in the bulk of the code - it's dangerous, hard to track and will bite you.

The way that I'd do this is to have a function called getDB() which can either be at class level by way of a constructor injection or static within a common class.

So the code becomes

class SomeClass {
    protected $dbc;

    public function __construct($db) {
        $this->dbc = $db;
    }

    public function getDB() {
        return $this->dbc;
    }

    function read_something() {
        $db = getDB();
        $db->query();
    }
}

or using a common shared class.

function read_something() {
    $db = System::getDB();
    $db->query();
}

No matter how much elegant system design you do, there are always a few items that are necessarily global in scope (such as DB, Session, Config), and I prefer to keep these as static methods in my System class.

Having each class require a connection via the constructor is the best way of doing this, by best I mean most reliable and isolated.

However be aware that using a common shared class to do this can impact on the ability to isolate fully the objects using it and also the ability to perform unit tests on these objects.