Use of PDO in classes

Question

I have a few classes that perform some MySQL queries and prepared statements. However, I am lost in how to incorporate my PDO object within those classes. For example, I want to do something like this:

<?php

$dbh = new PDO(...);

class Foo extends PDO {
    public $dbh;

    public function bar() {
        $this->dbh->prepare('SELECT * FROM table');
        $this->dbh->execute();

    }
}


?>

Unfortunately, it doesn't work. Can anyone suggest an elegant way to do this? Thanks for your time. Sorry I'm new to this, please leave any comments if you are unclear about anything and I'll do my best to respond!

Answer 1

$dbh isn't within the scope of Foo, do this instead:

class Foo /*extends PDO*/
{
    public $dbh;

    public function __construct()
    {
        $dbh = new PDO(/*...*/);
    }

    public function bar()
    {
        $this->dbh->prepare('SELECT * FROM table');
        return $this->dbh->execute();
    }
}

Also, Foo doesn't need to extend PDO.

Answer 2

You can instanciate your connection to the database in a class that implement the singleton pattern. The connection will be done once and this class will be easily accessible by all of your other objects / scripts.

i use a class called "Core" in the following exemple;

class Core
{
    public $dbh;   // handle of the db connexion
    private static $dsn  = 'mysql:host=127.0.0.1;dbname=mydb';
    private static $user = 'myuser';
    private static $pass = 'mypassword';


    public function __construct () {
      $this->dbh = new PDO(self::$dsn,self::$user,self::$pass);
    }

    public static function getInstance(){
        if(!isset(self::$instance)){
            $object= __CLASS__;
            self::$instance=new $object;
        }
        return self::$instance;
    }

    // others global functions
}

in all your scripts / objects you just have to get the instance of Core and then query the DB

$sql = "select login, email from users where id = :id";

try {
    $core = Core::getInstance();
    $stmt = $core->dbh->prepare($sql);
    $stmt->bindParam(':id', $this->id, PDO::PARAM_INT);

    if ($stmt->execute()) {
        $o = $stmt->fetch(PDO::FETCH_OBJ);
        // blablabla....

If you need more informations about singleton look at the php doc http://php.net/manual/en/language.oop5.patterns.php