Accessing a PDO instance from another class

Question

Here is my db class for connecting with database using pdo ext.

class db
{
    private $host;
    private $dbname;
    private $username;
    private $password;

    public function __construct($host,$db,$name,$pass)
    {
         $this->host=$host;
         $this->dbname=$db;
         $this->username=$name;
         $this->password=$pass;
         $dsn = 'mysql:'.$this->dbname.';'.$this->host;
         try 
         {
            $conn = new PDO($dsn, $this->username, $this->password);


            $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
         } 
         catch(PDOException $e) 
         {
              echo 'ERROR: ' . $e->getMessage();
         }
 }
}

I call db class in login class like this...

$host='localhost';
        $db='techy_issue_tracker';
        $name='root';
        $pass='';
        $base= new db($host,$db,$name,$pass);

Here is the problem, to make a pdo query inside login class (extending db class) if I use a line this...

$stmnt = $conn->prepare('SELECT id FROM users WHERE name :name OR email = :email');

It generates two errors, saying.. Notice: Undefined variable: conn... and Fatal error: Call to a member function prepare() on a non-object...

I can fix this by simply putting all pdo stuff inside login class but still I am just curious...how do you guys call an object (which is an instance of pdo class?) from another class.

PHP Class Based User System With PDO - Call to a member function prepare() on a non-object This question is interesting but didn't understand much :/

Didn't practice OOP much so some good explanation would be appreciated! Thanks.

Elliot B. Elliot B. · Accepted Answer · 2012-12-27T23:47:18

You need to intialize $conn as a public property of your db class.

After the private properties in your db class, add this:

public $conn;

Then, inside your try catch, change $conn to $this->conn:

$this->conn = new PDO($dsn, $this->username, $this->password);
$this->conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

Then, assuming you've correctly extended the db class, you can access conn in this manner:

$stmt = $db->conn->prepare('SELECT id FROM users WHERE name :name OR email = :email');

Accessing a PDO instance from another class

3 Answers