PHP and PDO class question

Question

I am very new to OOP styled PHP, and I am trying to implement PDO as well. I found this nice little class online which handles the database connection, however I have no ide

Answer 1

You should use Dependency Injection:

$steve = new Person($db_handle);

And yes, using the syntax you're hoping to avoid is the way to do it. You can always assign the class variable to a local method one by saying $dbh = $this->db_handle; which I believe is marginally faster.

Answer 2

If you really must do database work from inside your Person object (separation of concerns says that this should be taken care of elsewhere), you can either pass it as a constructor argument (based on your usage, it looks like that may be the way you want to go), or as a setter injection. For the former:

class Person
{
    function __construct($db_handle)
    {
        // ... your existing code

Then you instantiate your person object like so:

$person = new Person($db_handle);

That's really the only way you can avoid needing to use $this->db_handler without copying the variable into local scope.

Answer 3

There are (at least) three ways to handle this. The most portable, and oft recommended is called "dependency injection", whereby you pass the database handle into your class via its __construct() and store it in a class variable. Requires accessing it with $this->db like you didn't want to have to do.

class Person {
  // Member to hold the db handle
  public $db;

  public function __construct($db_handle) {
    // Assign the handle to a class member variable in the constructor
    $this->db = $db_handle;
  }
  public function otherFunc() {
    $this->db; // do something
  }
}

$person = new Person($db_handle);

Next method would be to instantiate the $db_handle inside the constructor rather than passing it in. This is a little harder to test and debug.

class Person {
   public $db;
   public function __construct() {
      $this->db = PDO_DBConnect::getInstance();
   }
}

Finally, you can call $db_handle as a global whenever you use it in your class. This is perhaps the hardest to read and debug.

class Person {
  public function __construct() {
    global $db_handle;
  }
  public function otherFunc() {
    global $db_handle;
    $db_handle; // do something
  }
}