Php 101: PDO

1. PHP 101: PDO or: How I Learned to Stop Worrying and Love Data Access Abstraction Jeremy Kendall | Memphis PHP | July 26, 2012

2. What is PDO? • PDO == PHP Data Objects • Lightweight, consistent interface for accessing databases in PHP • Provides data access abstraction, not database abstraction • Ships with PHP 5.1 • PECL extension for 5.0

3. Drivers include . . . • MySQL • PostgreSQL • SQL Server • SQLite • and more . . .

4. Which drivers do I have? • var_dump(PDO::getAvailableDrivers()); • If you don’t see what you need, check php.ini

5. Working with databases • Solved problem, you don’t have to write anything yourself • PHP and MySQL have an especially rich history • CRUD is the easy part • Creating clean, maintainable code is the challenge

6. Let’s look at some typical procedural code

7. What we’re building

8. mysql <?php $conn = mysql_connect('localhost', 'testuser', 'testpass') or die('Could not connect: ' . mysql_error()); mysql_select_db('bookshelf') or die('Could not select bookshelf'); $result = mysql_query('SELECT * FROM bookshelf ORDER BY title', $conn) or die('Invalid query: ' . mysql_error()); ?> <table> <tr> <th>Title</th><th>Author</th> </tr> <?php while ($row = mysql_fetch_assoc($result)) { echo "<tr>"; echo "<td>{$row['title']}</td><td>{$row['author']}</td>"; echo "</tr>"; } ?> </table> <?php mysql_close($conn);

14. Oops! Should have used mysqli!

15. mysqli <?php $conn = mysqli_connect('localhost', 'testuser', 'testpass', 'bookshelf') or die('Could not connect: ' . mysqli_connect_error()); $result = mysqli_query($conn, 'SELECT * FROM bookshelf ORDER BY title') or die('Invalid query: ' . mysqli_error($conn)); ?> <table> <tr> <th>Title</th><th>Author</th> </tr> <?php while ($row = mysqli_fetch_assoc($result)) { echo "<tr>"; echo "<td>{$row['title']}</td><td>{$row['author']}</td>"; echo "</tr>"; } ?> </table> <?php mysqli_close($conn);

16. Refactoring problems // You can't simply find and replace // because of differences in the interfaces // mysql_query wants query first and connection second $result = mysql_query($query, $conn); // mysqli_query is exactly opposite $result = mysqli_query($conn, $query);

19. Changing DB vendors? Have fun with that.

20. sqlsrv <?php $connectionInfo = array( 'Database' => 'bookshelf', 'UID' => 'testuser', 'PWD' => 'testpass' ); $conn = sqlsrv_connect('serverNameinstanceName', $connectionInfo); $stmt = sqlsrv_query($conn, 'SELECT * FROM bookshelf ORDER BY title'); ?> <table> <tr> <th>Title</th><th>Author</th> </tr> <?php while ($row = sqlsrv_fetch_array($stmt, SQLSRV_FETCH_ASSOC)) { echo "<tr>"; echo "<td>{$row['title']}</td><td>{$row['author']}</td>"; echo "</tr>"; } ?> </table> <?php sqlsrv_close($conn);

26. But what can you do about it?

27. You could roll your own <?php class MyDb { public function __construct($host, $username, $password, $dbname) { } public function query($sql, array $bind) { } // . . . }

28. Or don’t and use PDO

29. <?php $dsn = 'mysql:host=localhost;dbname=bookshelf'; $username = 'testuser'; $password = 'testpass'; $options = array( PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION, PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC ); try { $dbh = new PDO($dsn, $username, $password, $options); } catch (PDOException $e) { echo 'Error!: ' . $e->getMessage(); die(); } // $result is an array, so we can use array functions rather than db vendor functions $result = $dbh->query('SELECT * FROM bookshelf ORDER BY title')->fetchAll(); ?> <table> <tr> <th>Title</th><th>Author</th> </tr> <?php foreach ($result as $row) { echo "<tr>"; echo "<td>{$row['title']}</td><td>{$row['author']}</td>"; echo "</tr>"; } ?> </table>

36. But I’m going to use SQLite in DEV . . .

37. No problem! Change the dsn, username, and password. Done. $dsn = 'mysql:host=localhost;dbname=bookshelf'; $username = 'testuser'; $password = 'testpass'; becomes $dsn = 'sqlite:' . realpath('./data/db/bookshelf.db'); $username = null; $password = null;

38. Connecting • DSN required, username & pass optional • A connection error always throws an Exception, so use try/catch • Closing a connection is as simple as $dbh = null

39. Errors and Exceptions • Three error modes • PDO::ERRMODE_SILENT • PDO::ERRMODE_WARNING • PDO::ERRMODE_EXCEPTION • Always use exceptions • No, really, use exceptions

40. Insert, Update, Delete • PDO::exec() • Returns # rows affected • Won’t return results of SELECT • Won’t escape data (use PDO::quote())

41. Delete example /* quote string */ $title = $dbh->quote('Refactoring'); /* Delete a book */ $count = $dbh->exec("DELETE FROM bookshelf WHERE title = $title"); /* Return number of rows that were deleted */ print("Deleted $count rows.n");

45. In almost all cases, favor prepared statements over PDO::exec()

46. Prepared statements • To know them is to love them • No more SQL injection • Can execute same statement multiple times with different values • Efﬁcient (in most cases) • Positional, named • The one feature PDO emulates

47. Prepared statements Using named parameters: $sql = "INSERT INTO bookshelf (title, author) VALUES (:title, :author)"; $statement = $dbh->prepare($sql); $statement->bindParam('title', $title); $statement->bindParam('author', $author); $books = array( "Clean Code" => "Robert C. Martin", "Refactoring" => "Martin Fowler", "Test-Driven Development" => "Kent Beck", "The Agile Samurai" => "Jonathan Rasmusson", "Working Effectively with Legacy Code" => "Michael Feathers" ); foreach ($books as $title => $author) { $setup->execute(); }

51. Prepared statements Using positional parameters: $sql = "INSERT INTO bookshelf (title, author) VALUES (?, ?)"; $statement = $dbh->prepare($sql); $statement->bindParam(1, $title); $statement->bindParam(2, $author); $books = array( "Clean Code" => "Robert C. Martin", "Refactoring" => "Martin Fowler", "Test-Driven Development" => "Kent Beck", "The Agile Samurai" => "Jonathan Rasmusson", "Working Effectively with Legacy Code" => "Michael Feathers" ); foreach ($books as $title => $author) { $setup->execute(); }

52. Prepared statements Array of named params to PDO::execute $sql = "INSERT INTO bookshelf (title, author) VALUES (:title, :author)"; $statement = $dbh->prepare($sql); $statement->execute(array('title' => $title, 'author' => $author));

55. Select • Gets data from the database • Results returned as PDOStatement • How data is fetched from statement depends on fetch mode • Grab all results at once with fetchAll()

56. Fetch modes • Can be set in constructor or later with PDO::setAttribute() or PDOStatement::setFetchMode() • PDO::FETCH_ASSOC • PDO::FETCH_BOTH (default) • PDO::FETCH_NUM • PDO::FETCH_OBJ • to name a few . . .

57. Fetching // Gets all books in database $stmt = $dbh->query("SELECT * FROM bookshelf ORDER BY title"); // Returns array of all results $books = $stmt->fetchAll(); // Returns next row in manner determined by fetch mode $row = $stmt->fetch(); // Can choose fetch mode at time of fetch $row = $stmt->fetch(PDO::FETCH_OBJ);

62. Fetching PDOStatement implements Traversable, which allows you to: $stmt = $dbh->query('SELECT * FROM bookshelf ORDER BY title'); ?> <table> <tr> <th>Title</th><th>Author</th> </tr> <?php foreach ($stmt as $row) { echo "<tr>"; echo "<td>{$row['title']}</td><td>{$row['author']}</td>"; echo "</tr>"; } ?> </table>

63. Fetching PDOStatement implements Traversable, which allows you to: $stmt = $dbh->query('SELECT * FROM bookshelf ORDER BY title'); ?> <table> <tr> <th>Title</th><th>Author</th> </tr> <?php foreach ($stmt as $row) { echo "<tr>"; echo "<td>{$row['title']}</td><td>{$row['author']}</td>"; echo "</tr>"; } ?> </table>

64. Fetching PDO::FETCH_BOUND is slick $stmt = $dbh->query('SELECT id, title, author FROM bookshelf ORDER BY title'); $stmt->bindColumn('title', $title); $stmt->bindColumn('author', $author); ?> <table> <tr> <th>Title</th><th>Author</th> </tr> <?php while ($stmt->fetch(PDO::FETCH_BOUND)) { echo "<tr>"; echo "<td>$title</td><td>$author</td>"; echo "</tr>"; } ?> </table>

67. But wait, there’s more!

68. PDO::lastInsertId() • Returns the ID of the last inserted row • Or the last value from a sequence object • Be careful, some databases don’t support this and may exhibit unexpected behavior

69. Transactions • PDO::beginTransaction() • PDO::commit() • PDO::rollback() • Check your DB documentation for support

70. Beneﬁts • Maintainability • Portability (with a few vendor speciﬁc caveats) • Safety (prepared statements) • Object oriented

71. Drawbacks • Not all vendor speciﬁc features supported • Interface is almost the same for all databases • Slower in some cases • Mediocre Oracle support (who uses Oracle?)

72. Portable, mostly • Every DB has its own oddities and gotchas • PDO offers data access abstraction • You’ll likely still have to tweak if you’re doing anything other than very simple CRUD • Still better than mysql_*, mysqli_*, sqlsrv_* • Choose a DBAL like Doctrine if you need more

73. Credits • PHP Data Objects by Wez Furlong: http:// www.slideshare.net/wezfurlong/php-data-objects • Nettuts+: http://net.tutsplus.com/tutorials/php/why-you- should-be-using-phps-pdo-for-database-access/ • Introduction to PDO: http://www.dreamincode.net/ forums/topic/214733-introduction-to-pdo/ • php.net: http://us.php.net/manual/en/class.pdo.php

74. Questions?

75. Thanks! • @JeremyKendall • jeremy@jeremykendall.net • http://about.me/jeremykendall

Php 101: PDO

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