PHP variable scope: passing external objects to a class

Question

I'm defining models that share a common database. However, I'm having trouble passing a PDO object via require_once(). I'm getting the following error:

Fatal error: Call to a member function prepare() on a non-object...

I'm guessing this is just a scope issue. I tried declaring $database as a global in both files but that didn't seem to work. Any ideas?

common.php

$host = 'localhost';
$dbname = 'database';
$username = 'user';
$password = 'pass';

$database = new PDO("mysql:host=$host;dbname=$dbname", $username, $password, array(PDO::ATTR_PERSISTENT => true));

product.php

require_once('common.php');

class Product {

  function fetch_from_category($category) {
    $query = $database->prepare('SELECT * FROM product WHERE product.category = ?');
    $query->execute($category);
    return $query->fetchAll(PDO::FETCH_ASSOC);
  }

}

$database is defined outside the class; and, similar to normal functions, you can't see the variable inside a class. Either pass it to the class as MrCode suggested or set it as global ( not recommended though ) as Rawkode suggested. — Peon
– Peon, Commented Nov 27, 2012 at 12:42

deceze · Accepted Answer · 2012-11-27 12:42:03Z

1

It is indeed a scope issue, $database is not defined inside Product::fetch_from_category. You should pass it into the object when instantiating it:

class Product {

  protected $database;

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

  public function fetch_from_category($category) {
      $query = $this->database->prepare('SELECT * FROM product WHERE product.category = ?');
      $query->execute($category);
      return $query->fetchAll(PDO::FETCH_ASSOC);
  }

}

...

require_once 'common.php';
require_once 'product.php';

$product = new Product($database);

answered Nov 27, 2012 at 12:42

deceze♦

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MrCode · Accepted Answer · 2012-11-27 12:41:29Z

1

Pass $database to the class, then store it as a property and access with $this->database:

class Product {

  protected $database;

  public function setDb($db)
  {
      $this->database = $db;
  }

  function fetch_from_category($category) {
    $query = $this->database->prepare('SELECT * FROM product WHERE product.category = ?');
    $query->execute($category);
    return $query->fetchAll(PDO::FETCH_ASSOC);
  }

}

$p = new Product();
$p->setDb($database);

answered Nov 27, 2012 at 12:41

MrCode

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