Database Design Patterns with PHP 5.3

This session introduces most well known design patterns to build PHP classes and objects that need to store and fetch data from a relational databases. The session will describe the difference between of the Active Record, the Table and Row Data Gateway and the Data Mapper pattern. We will also examine some technical advantages and drawbacks of these implementations. This talk will expose some of the best PHP tools, which ease database interactions and are built on top of these patterns.

Transcript

2. Enterprise Database Design Patterns in PHP Hugo Hamon – OSIDays 2011
3. By Martin Fowler §  Table Module §  Transaction Script §  Row Data Gateway §  Table Data Gateway §  Active Record §  Data Mapper §  Unit of Work §  Identity Map §  Data Transfer Object §  …
4. Table Data Gateway
5. « An object that acts as a Gateway to a database table. One instance handles all the rows in the table. » Martin Fowler  
6. Same as Data Access Object Martin Fowler  
7. CRUD
8. $table = new OrderGateway(new Connection('...')); $table->insert('XX123456789', 358.80, 'unpaid'); $table->update(42, 'XX123456789', 358.80, 'paid'); $table->delete(42);
9. class OrderGateway { private $conn; public function __construct(Connection $conn) { $this->conn = $conn; } }
10. class OrderGateway { public function insert($reference, $amount, $status) { $query = 'INSERT INTO orders (reference, amount, status) VALUES (?, ?, ?)'; $data = array($reference, $amount, $status); $this->conn->executeQuery($query, $data); return $this->conn->lastInsertId(); } }
11. class OrderGateway { public function update($pk, $ref, $amount, $status) { $query = 'UPDATE orders SET reference = ?, amount = ?, status = ? WHERE id = ?'; $data = array($ref, $amount, $status, $pk); return $this->conn->executeQuery($query, $data); } }
12. class OrderGateway { public function delete($pk) { return $this->conn->executeQuery( 'DELETE FROM orders WHERE id = ?', array($pk) ); } }
13. Finders
14. $orders = $table->findAll(); $orders = $table->findPaidOrders(); $orders = $table->findUnpaidOrders(); $orders = $table->findBy(array( 'status' => 'paid', 'amount' => 250.00 )); $order = $table->find(42); $order = $table->findOneBy(array('reference' => '...'));
15. class OrderGateway { public function findAll() { $query = 'SELECT * FROM orders'; return $this->conn->fetchAll($query); } public function find($pk) { $rs = $this->conn->findBy(array('id' => $pk)); return 1 === count($rs) ? $rs[0] : false; } }
16. public function findBy(array $criteria) { $where = array(); foreach ($criteria as $field => $value) { $where[] = sprintf('%s = ?'); } $q = sprintf( 'SELECT * FROM orders WHERE %s', implode(' AND ', $where) ); return $this->conn->fetchAll($q, array_values($criteria)); }
17. public function findPaidOrders() { return $this->findBy(array('status' => 'paid')); } public function findUnpaidOrders() { return $this->findBy(array('status' => 'unpaid')); }
18. When to use it?
19. Row Data Gateway
20. « An object that acts as a Gateway to a single record in a data source. There is one instance per row. » Martin Fowler  
21. CRUD
22. class Order { private $id; private $reference; private $amount; private $vat; private $total; private $createdAt; // Getters and setters for each property // ... }
23. $conn = new Connection('...'); $order = new OrderGateway(); $order->setReference('XX12345678'); $order->setAmount(300.00); $order->setVat(58.80); $order->setTotal(358.80); $order->setCreatedAt(new DateTime()); $order->insert($conn);
24. class OrderGateway { public function insert(Connection $conn) { $query = 'INSERT INTO orders (reference, amount, vat, total, created_at) VALUES (?, ?, ?, ?, ?)'; $data = array( $this->reference, $this->amount, $this->vat, $this->total, $this->createdAt->format('Y-m-d H:i:s') ); $conn->executeQuery($query, $data); $this->id = $conn->lastInsertId(); } }
25. Finders
26. OrderFinder::setConnection($conn); $order = OrderFinder::findByReference('XX12345678'); echo sprintf('%01.2f euros', $order->getTotal());
27. class OrderFinder { static public function findByReference($reference) { $query = 'SELECT * FROM orders WHERE reference = ?'; $rs = static::getConnection() ->fetchSingle($query, array($reference)) ; return $rs ? OrderGateway::load($rs) : false; } }
28. class OrderGateway { static public function load(array $rs) { $order = new OrderGateway($rs['id']); $order->setReference($rs['reference']); $order->setAmount($rs['amount']); $order->setVat($rs['vat']); $order->setTotal($rs['total']); $order->setCreatedAt(new DateTime($rs['created_at'])); return $order; } }
29. OrderFinder::setConnection($conn); $orders = OrderFinder::findMostExpensiveOrders(10); foreach ($orders as $order) { echo $order->getReference(), "\n"; echo sprintf('%01.2f euros', $order->getTotal()), "\n"; echo "\n-----\n"; }
30. class OrderFinder { static public function findMostExpensiveOrders($limit) { $orders = array(); $query = 'SELECT * FROM orders ORDER BY total DESC LIMIT ?'; $rs = static::getConnection()->fetchAll($query, array($limit)); foreach ($rs as $data) { $orders[] = OrderGateway::load($data); } return $orders; } }
31. When to use it?
32. Active Record
33. « An object that wraps a row in a database table or view, encapsulates the database access, and adds domain logic on that data. » Martin Fowler  
34. Active Record = Row Data Gateway + Business Logic
35. Active Record = Data + Behaviors
36. Active Record = Properties + Methods
37. class Order { private $id; private $reference; private $amount; private $vat; private $vatRate; private $total; private $createdAt; private $status; private $isPaid; // Getters and setters for each property // ... }
38. class Order { public function __construct($id = null) { if (null !== $id) { $this->id = $id; } $this->vatRate = 0.00; $this->vat = 0.00; $this->amount = 0.00; $this->total = 0.00; $this->isPaid = false; $this->status = 'processing'; $this->createdAt = new DateTime(); } }
39. $conn = new Connection('...'); $order = new Order(); $order->setReference('XX12345678'); $order->setAmount(300.00); $order->setVatRate(0.196); $order->applyDiscount(20.00); $order->updateTotal(); $order->save($conn);
40. class Order { public function applyDiscount($discount) { $this->amount -= $discount; } public function updateTotal() { if ($this->vatRate) { $this->vat = $this->amount * $this->vatRate; } $this->total = $this->amount + $this->vat; } }
41. class Order { public function isPaid() { return $this->isPaid; } public function setPaid() { $this->isPaid = true; } }
42. class Order { public function isReadyForShipment() { return $this->isPaid() && 'complete' == $this->status; } public function ship($address) { $this->doShipment($address); $this->status = 'shipped'; } }
43. class OrderController { public function confirmAction($reference) { $conn = $this->getDatabaseConnection(); $order = ...; $order->setPaid(); $order->save($conn); if ($order->isReadyForShipment()) { $order->ship(); return $this->view->render('ship.php', array('order' => $order)); } return $this->view->render('pending.php', array('order' => $order)); } }
44. Refactoring
45. abstract class ActiveRecord { protected $fields = array(); abstract public function getTableName(); public function save(Connection $conn) { // insert or update $fields in the database } public function delete(Connection $conn) { // delete the object from the database } }
46. class Order extends ActiveRecord { private $amount; abstract public function getTableName() { return 'tbl_orders'; } public function setAmount($amount) { $this->amount = $amount; $this->fields['amount'] = $amount; } }
47. When to use it?
48. Data Mapper
49. « A layer of Mappers that moves data between objects and a database while keeping them independent of each other and the mapper itself. » Martin Fowler  
50. « Man in the Middle »
51. http://martinfowler.com  
52. class OrderMapper { private $conn; public function __construct(Connection $conn) { $this->conn = $conn; } public function store(Order $order) { // Execute the query to persist the object to the DB } public function remove(Order $order) { // Executes the query to remove the object to the DB } }
53. $order = new Order(); $order->setReference('XX12345678'); $order->setAmount(300.00); $order->setVatRate(0.196); $order->updateTotal(); $conn = new Connection('mysql:host=localhost ...'); $mapper = new OrderMapper($conn); $mapper->store($order);
54. class OrderMapper { public function findAll() { $objects = array(); $query = 'SELECT id, reference, vat ... FROM orders'; foreach ($this->conn->fetchAll($query) as $data) { $object = new Order($data['id']); $object->load($data); $objects[] = $object; } return $objects; } }
55. class OrderMapper { public function find($pk) { $query = 'SELECT id, vat ... FROM orders WHERE id = ?'; $object = false; if (false !== $data = conn->fetch($query, array($pk))) { $object = new Order($data['id']); $object->load($data); } return $object; } }
56. $conn = new Connection('mysql:host=localhost ...'); $mapper = new OrderMapper($conn); $order = $mapper->find(42); $order->setAmount(399.00); $order->updateTotal(); $mapper->store($order);
57. Unit testing
58. class OrderTest extends PHPUnit_Framework_TestCase { public function testUpdateTotal() { $order = new Order(); $order->setAmount(299.00); $order->setVatRate(0.196); $order->updateTotal(); $this->assertEquals(58.60, $order->getVat()); $this->assertEquals(357.60, $order->getTotal()); } }
59. When to use it?
60. IdentityMap
61. « Ensures that each object gets loaded only once by keeping every loaded object in a map. » Martin Fowler  
62. $conn = new Connection('mysql:host=localhost ...'); $mapper = new OrderMapper($conn); $orderA = $mapper->find(42); $orderB = $mapper->find(42); $orderC = $mapper->find(42); // 3 SQL queries for getting the same object
63. The solution
64. class IdentityMap implements IdentityMapInterface { private $entities; public function fetch($class, $pk) { $key = $this->getKey($class, $pk); if (isset($this->entities[$key])) { return $this->entities[$key]; } return false; } }
65. class IdentityMap implements IdentityMapInterface { public function store(ValueObjectInterface $entity) { $key = $this->getKey($class, $entity->getId()); $this->entities[$key] = $entity; } private function getKey($class, $pk) { return $class.'-'.$pk; } }
66. class Order implements ValueObjectInterface { private $id; private $reference; private $amount; // ... public function getId() { return $this->id; } }
67. class OrderMapper extends DatabaseMapper { private $map; public function __construct(IdentityMap $map, ...) { parent::__construct($conn); $this->map = $map; } }
68. class OrderMapper extends DatabaseMapper { public function store(Order $order) { parent::store($order); $this->map->store('Order', $object); } }
69. class OrderMapper extends DatabaseMapper { public function find($pk) { if (false !== $object = $this->map->fetch($pk)) { return $object; } if (false !== $object = parent::find($pk)) { $this->map->store('Order', $object); } return $object; } }
70. $conn = new Connection('mysql:host=localhost ...'); $mapper = new OrderMapper(new IdentityMap(), $conn); $orderA = $mapper->find(42); // Query $orderB = $mapper->find(42); // No query $orderB->setAmount(299.00); $orderB->setVatRate(0.196); $orderB->updateTotal(); $mapper->store($orderB); $orderC = $mapper->find(42); // No query
71. Query Object
72. $query = Query::create() ->select(array('id', 'reference', 'amount', 'status')) ->from('orders') ->where(Criteria::equals('status', 'paid')) ->where(Criteria::greaterThan('amount', 2000)) ->where(Criteria::like('reference', 'XX123%')) ->orderBy('amount', 'desc') ->getSql() ; // SELECT id, reference, amount, status // WHERE status = ? AND amount > ? AND reference LIKE ? // ORDER BY amount DESC
73. class Criteria { private $field; private $operator; private $parameters; public function __construct($field, $operator, $value) { $this->field = $field; $this->operator = $operator; $this->parameters[] = $value; } }
74. class Criteria { static public function equal($field, $value, $vars) { return new Criteria($field, '=', $vars); } static public function notEqual($field, $value, $vars) { return new Criteria($field, '<>', $vars); } }
75. Custom Queries
76. class OrderQuery extends Query { public function filterByPriority($amount) { return $this ->where(Criteria::equal('status', 'paid')) ->where(Criteria::greaterThan('amount', $amount)) ; } public function filterByReference($like) { return $this->where(Criteria::like('reference', $like)); } }
77. $query = OrderQuery::create() ->filterByPriority(2000) ->filterByReference('%567%') ->orderByAmount('DESC') ->getSql() ;
78. ORM Tools
79. Zend_DB Doctrine 1.2 Doctrine 2.x Propel Pomm
80. Quizz Can you guess the patterns?
81. $table = new Author(); // New empty row $row = $table->createRow(); // Insert a new row $row->firstName = 'Jules'; $row->lastName = 'Verne'; $row->save();
82. $pax1 = new Passenger('Hugo Hamon', '7B'); $pax2 = new Passenger('John Smith', '3A'); $aircraft = new Plane(); $aircraft->setCapacity(120); $aircraft->addPassenger($pax1); $aircraft->addPassenger($pax2); $aircraft->save(); $pax2->changeSeat('2C'); $pax2->save(); $aircraft->isAvailableSeat('3A') ? 'Yes' : 'No';
83. $post = new BlogPost(); $post->setTitle('My First Blog Post'); $post->setBody('Some content...'); $author = new Author(); $author->setName('Hugo Hamon'); $author->addPost($post); $em->persist($user); $em->persist($post); $em->flush();
84. $data = array( 'first_name' => 'Jules', 'last_name' => 'Vernes', ); $table = new AuthorTable(); $table->insert($data);
85. Conclusion
86. By Martin Fowler §  Table Module §  Transaction Script §  Row Data Gateway §  Table Data Gateway §  Active Record §  Data Mapper §  Unit of Work §  Identity Map §  Data Transfer Object §  …
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