PHP Advanced and Object-Oriented Programming (2013)

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3. Begin defining the User class:

class User implements iCrud {
private $_userId = NULL;
private $_username = NULL;

The User class implements iCrud, which means it must define the four methods identified in the interface. To demonstrate this concept, without overwhelming you with code, I’m going to define just two attributes in the class, both of which will be private.

4. Define the constructor:

function _ _construct($data) {
$this->_userId = uniqid();
$this->_username = $data['username'];
} // End of constructor.

The constructor is going to take an array of data as its lone argument. It will use this data to assign values to the internal private variables. Logically, you’d want to add some validation to the provided data here, too.

The constructor also creates a unique user ID value by invoking the PHP uniqid() function.

In a real-world application, the constructor might instead create a new user record in a database and assign the automatically generated primary key value to the internal attribute.

5. Define the create() method:

function create($data) {
self::_ _construct($data);
}

By implementing the iCrud interface, this class is forced to have a create() method that takes a single argument. However, the constructor already does what’s required to create a new object of this type, so this method can just call the constructor (using the keyword self, which refers to the current class, plus the scope resolution operator), passing along the provided data.

This method would be used in situations where a new User object is created (perhaps thereby creating a new record in the database) and later reused to create a new record.

6. Define the read() method:

function read() {
return array('userId' => $this->_userId, 'username' => $this->_username);
}

The read() method takes no arguments and returns an array of information. In this hypothetical example, the information is represented by internal variables. In a real-world application, the read() method might fetch the associated information from the database, using the internal, private ID value to know which record to fetch.

7. Define the update() method:

function update($data) {
$this->_username = $data['username'];
}

Presumably, the user ID value cannot be updated, so the update() method as written only updates a single internal attribute. Again, you’d want to use proper validation here, instead of assuming that $data['username'] exists.

8. Define the delete() method and complete the class:

public function delete() {
$this->_username = NULL;
$this->_userId = NULL;
}
} // End of User class.

The delete() method clears out the values of the attributes. In a real-world example, it might delete the corresponding record from the database instead.

9. Create a new User object:

$user = array('username' => 'trout');
echo "<h2>Creating a New User</h2>";
$me = new User($user);

To make the interface more useful, two of its methods expect to receive a single argument, which would be an array of data. If the User class also stored an email address and password, those would be represented in this one array, too.

10. Get the user’s ID:

$info = $me->read();
echo "<p>The user ID is {$info['userId']}.</p>";

The read() method fetches the object’s information, returned as an array.

11. Change the user’s name and then confirm the change:

$me->update(array('username' => 'troutster'));
$info = $me->read();
echo "<p>The user name is now {$info['username']}.</p>";

12. Delete the record:

$me->delete();

Note that this line does not get rid of the User object. It only clears out the internally stored values.

13. Complete the page:

unset($me);
?>
</body>
</html>

14. Save the file as interface.php, place it in your Web directory, and test in your Web browser .

The output from using a User object that implements the iCrud interface.