Extend PDO class

Question

I want to start using PDO (switching from MySQL extension) and I would like to add some methods but to still have the entire PDO functionality. I would like to implement a function like this:

$db->getAll("SELECT * FROM table WHERE field1=:foo AND field2=:baz", array('foo'=>$foo, 'baz'=>$baz));

I think the best way is to extend the PDO class but in this case I would not have the instance of the class to be able to use it inside the class. Any idea?

Answer 1

I would advise against extending PDO, but rather creating a library/wrapper around it which other ORM's do.

I will construct your example code into a simple class for explanation.

class MyDB
{

    private $pdo;

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

    public function getAll($query, array $params)
    {
        $statement = $this->pdo->prepare($query);
        $statement->execute($params);
        return $statement->fetchAll();
    }

    public function getPdo()
    {
        return $this->pdo;
    }

    /**
     * This is called if the method cannot be found.
     * Pass it to PDO to handle.
     *
     * @param $name
     * @param $arguments
     */
    public function __call($name, $arguments)
    {
        return call_user_func(array($this->pdo, $name), $arguments)
    }

}

If you really want to access PDO directly then I've included a magic method but I don't recommend you take that route. See http://www.php.net/manual/en/language.oop5.magic.php

Doing this sort of stuff is fun for learning, but if you want a serious ORM then take a look at this SO question Good PHP ORM Library? and also research yourself.

Answer 2

Just before you get deep in your project here is an advice for you. Do it with ORM library.

For example I am doing the same thing you need with ORM library (in this case called db.php) like this:

$database->path->to->table->handler->load (\db\by('field1',$value1)->by('field2',$field2));

The complicated thing with ORMs are that they need class definitions to work with tables and many PHP developers are afraid of class definitions for their data objects. For above example to work you should have needed a class definition something like this:

namespace \path\to;
class table
{
    public $field1;
    public $field2;
}

And database initialization in case of db.php ORM library like this:

$database = new \db\database ('mysql:host=127.0.0.1', 'test_db', 'root', '1234');

And class attaching to database object to handle like this:

$database->add ('\path\to\table');

Additionally many ORMs have a magic method allowing you to automatically create or generate tables according your class definitions, for example db.php (http://dbphp.net) method:

$database->update();

Will create path_to_table table in your actual mysql database with 2 fields field1 and field2.

I am not sure why people should be afraid ORMs in PHP development they make life easier for everybody and give abilities not to get confused in your own code when you are working on large scale projects.

I believe sometimes this answer will save at least 1 human from future sufferings.

: D

Answer 3

a singleton example:

class DB
{
    protected static $instance = null;

    final private function __construct() {}
    final private function __clone() {}

    public static function instance()
    {
        if (self::$instance === null)
        {
            $dsn = 'mysql:host='.DB_HOST.';dbname='.DB_NAME;
            self::$instance = new PDO($dsn, DB_USER, DB_PASS);
            self::$instance->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        }
        return self::$instance;
    }
    public static function __callStatic($method, $args) {
        return call_user_func_array(array(self::instance(), $method), $args);
    }

    public static function getAll($sql, $data = NULL, $mode = PDO::FETCH_ASSOC)
    {
        $stmt = self::instance()->prepare($sql);
        $stmt->execute($data);
        return $stmt->fetchAll($mode);
    }
}

$sql  = "SELECT * FROM table WHERE field1=:foo AND field2=:baz";
$data = DB::getAll($sql, array('foo'=>$foo, 'baz'=>$baz));