How to share MySQL connection over class in PHP?

Question

I want to share a MySQL connection, with other class within PHP, which held the query to do. So MySQL.php contains:

    <?php
$user = 'username';
$passowrd = 'password';
$conn = new PDO('mysql:host=ip;dbname=DBName;port=3306',$user,$passowrd);
?>

And the php file, which I call MyLibrary.php contains:

    <?php
include 'DB.php';

class Manager {

    function jsonQuery() {

        $response = array ();


        $st = $conn->query ( "query");

        $response ["results"] = array ();

        foreach ( $st->fetchAll () as $row ) {

            //my stuff with the query
        }

        $response ["success"] = 1;

        echo json_encode ( $response );
    }

}

$object = new Manager();

$object->jsonQuery();

?>

So how can I do ?

You don't want to keep the database connection open and share it across different modules of your project. Instead you include the file that opens the database (i.e. `MySQL.php`) wherever you need database access and close it after your queries. — Haensl, Jul 02 '15 at 12:35
You can make a class for the connect that have a variable, maybe a controller, and then always extend that. Just remember to make a __construct in the controller that makes the variable to the PDO connection — Jesper, Jul 02 '15 at 12:36
I believe what you are after is something called the [singleton pattern](https://en.wikipedia.org/wiki/Singleton_pattern), but could equally be done with a static class. — Phylogenesis, Jul 02 '15 at 12:36

score 3 · Accepted Answer · edited May 23 '17 at 11:44

3

It's called dependency injection and it's simple to implement. You pass the parameter into your class directly when you instantiate it. This way you never implement it more than once and you share that instance across your codebase

class Manager {
    /** @var \PDO */
    protected $pdo;

    public function __construct(\PDO $pdo) {
        $this->pdo = $pdo;
    }

    public function jsonQuery() {
        $response = array ();
        $st = $this->pdo->query("query");
        $response ["results"] = array();

        foreach ( $st->fetchAll() as $row ) {
            //my stuff with the query
        }

        $response ["success"] = 1;
        echo json_encode($response);
    }
}

$object = new Manager($conn);

edited May 23 '17 at 11:44

Community

1
1

answered Jul 02 '15 at 12:39

Machavity

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you cant't use $this->pdo in static functions – Frank Jul 02 '15 at 12:43
@Frank No, you can't. But this question doesn't deal with statics and you can still use injection with static methods. – Machavity Jul 02 '15 at 12:44
How Can I deal with $object->jsonQuery(); ? Can you put all the code of class Manager, with $conn variable ? – I love coding Jul 02 '15 at 12:53
@Ilovecoding I added the rest of your code into the example – Machavity Jul 02 '15 at 12:56
It works ! It is a good choice to get access to a DB with this solution ? – I love coding Jul 02 '15 at 12:56
I use this methodology myself in my own code base. it's easier to understand and work with because you never have to track down a global variable. – Machavity Jul 02 '15 at 12:57

Frank · Answer 2 · 2015-07-02T14:33:09.303

0

I think the best way is to use a function, it is allways global :-)

Simple sample:

function &pdo() {
  $user = 'username';
  $passowrd = 'password';
  static $db = null;
  if($db===null)
    $db = new PDO('mysql:host=ip;dbname=DBName;port=3306',$user,$passowrd);
  return $db;
}

Alternative, but not good: use global:

function foo() {
  global $conn;
  # your code ....
}

or

$GLOBALS['conn'];

It is allways present.

edited Jul 02 '15 at 14:33

answered Jul 02 '15 at 12:37

Frank

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Globals are generally [something to avoid](http://stackoverflow.com/questions/12445972/stop-using-global-in-php) – Machavity Jul 02 '15 at 12:46
Do you mean to put function &pdo in DB.php ? – I love coding Jul 02 '15 at 12:52
yes, simply put the function in DB.php and use it in your code. – Frank Jul 02 '15 at 14:32

How to share MySQL connection over class in PHP?

2 Answers2