PDO (PHP Data Objects) - Starter Guide

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It may surprise you to hear, that using the mysql_connect() function in PHP has recently be marked as "old hat" coding because it's slow in comparison with newer methods. A better alternative is PDO (PHP Data Objects), a lightweight method for accessing databases. Here is a quick overview to help you get started with PDO.

Reasons to use PDO

  • It's Fast - it talks to the database via a database specific PDO-driver.
  • It's Object Oriented - The methods within the class are the same for each database driver, so you can easily change your database driver without lots of extra coding.
  • It's Flexible-  You can easily change between such database drivers as PostgreSQL, MySQL or SQLite by pretty much just changing your construct statement.
  • It's Safer - PDO encourages you to bind parameters to your SQL query's, meaning that it's significantly less likely your website will suffer from a SQL injection based attack.

Connecting to a Database

Connecting to a database is pretty simple. Here is how to connect to a MySQL Database.

// Define the parameters
$host = 'localhost';
$dbname = 'my_database';
$user = 'mysql_username';
$pass = 'mysql_password';

try {
  // Call the PDO class.
  $db= new PDO('mysql:host='.$host.';dbname='.$dbname, $user, $pass);
} catch(PDOException $e) {
  // If something goes wrong, PDO throws an exception with a nice error message.
  echo $e->getMessage();


Doing A Query

Again, doing a query is just as simple as:

$query = $db->query('SELECT * FROM `users` ORDER BY ID DESC;');
$result = $query->fetchAll(PDO::FETCH_ASSOC);

// $result will now contain an object of all the rows in the table 'Users'

However, if you are using user variables which may cause a SQL Injection you should bind the parameter to the query (see next example).

Binding a parameter to a query

$query = $db->prepare('SELECT * FROM `users` WHERE `ID` = :ID: AND `email` = :email: ORDER BY ID DESC LIMIT 0,1;');
$query->execute(array(':ID:' => '3', ':email:' => 'me@email.com'));
$result = $query->fetchAll(PDO::FETCH_ASSOC);

If you bind a parameter to a request, it will sterilize the input so that it will not cause a SQL Injection.

Useful Resources

PHP Manual: PHP Data Objects Nettuts+: Why you Should be using PHP’s PDO for Database Access


As of PHP 5.4 the MySQL extension will be softly deprecated. This means you really should start using PDO ASAP!

This was written by Mike Rogers, a freelance Ruby on Rails developer based in London.

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If you want to discuss this post, feel free to tweet me (@MikeRogers0) or drop me an email. Any code samples unless stated otherwise are licensed under the The MIT License (MIT). Spotted a mistake? Send me a pull request :)