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What is PDO?

Last updated on
August 4, 2016 - 17:50

PDO is an acronym for PHP Data Objects. PDO is a lean, consistent way to access databases. This means developers can write portable code much easier. PDO is not an abstraction layer like PearDB. PDO is a more like a data access layer which uses a unified API (Application Programming Interface).

How to enable PDO

To enable PDO, configure --enable-pdo and --with-pdo-sqlite --with-pdo-mysql or whatever database needs supporting by PDO (see the PHP manual for more information).

Windows users

  • For Apache, you will need to make sure php_pdo.dll and php_pdo_mysql.dll exist in the php/ext directory, un-comment or add the appropriate lines in php.ini, and restart the web server.

    Under Windows, it may no longer be required to enable PDO when using newer versions of PHP, namely, PHP version 5.3 and later. This refers to php_pdo.dll. However, you still need to activate php_pdo_mysql.dll for MySQL or for whichever database you're using.

  • For IIS, PDO DLLs are not enabled by default. The preferred method for enabling them is to go to the Control Panel | Add/Remove Programs, highlight your PHP installation and click "Change" (Change/Remove - XP). Specify "FastCGI", then modify the installed extensions to include these two, then restart your server.

Macintosh users

Method 1

OS X 10.5: Detailed, step-by-step instructions are available here:

OS X 10.6: OS 10.6 comes with the PDO extension enabled by default. (For instructions on configuring your development environment, see:
Drupal 6 on OS X 10.6

Method 2

MAMP comes pre-configured with the PDO extension. For more information, see: HowTo: Create a local environment using MAMP.

Linux users

PDO is enabled by default as of php 5.1.0 on most linux systems. There is documentation to enable PDO for a mysql specific-driver.


As with most Linux systems, PDO support is present in PHP5 in all recent Ubuntu distributions, and certainly in PHP 5.2 which is required for Drupal 7. If you find that PDO support is not enabled, install the following packages and restart the server.

sudo apt-get install php5-common php5-mysql
sudo /etc/init.d/apache2 reload

Before restarting the server, make sure that extension=pdo.so and extension=pdo_mysql.so are being loaded, either in the php.ini file or in their own .ini files inside /etc/php5/conf.d.


If you find that PDO support is not enabled, do the following through SSH

yum update php-mysql
If bash tells you that pdo-mysql is not installed, then
yum install php-mysql

then restart your httpd/apache. When you try run the drupal installation script, you should be able to setup your MySQL database

Through WHM

  1. Go to Software > Easy Apache > Exhaustive Options List
  2. Select PDO and PDO MYSQL
  3. Save


Do not use the PECL PDO installer. The project is horribly outdated and abandoned. (See http://pecl.php.net/package/PDO.) Cases have been reported where PECL PDO support seems enabled but it doesn't work correctly. One symptom was the inability to install Drupal 7.

If you have already installed PECL PDO, you will need to remove it and then reinstall the version from PHP core, or ask your hosting provider to do so.

On Debian and Ubuntu, the required commands are:

sudo pecl uninstall pdo_mysql
sudo pecl uninstall pdo
sudo apt-get install --reinstall php5-common php5-mysql
sudo /etc/init.d/apache2 reload