Fatal error: Class 'PDO' not found in /home/.../public_html/drupal/includes/database/database.inc on line 184 Fatal error:

I have just installed Drupal 7 & have been having memory problems whilst in admin tasks, particularly with the Views module which completely failed to save a new view I was trying to create.

The error was:
Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 122880 bytes) in /home/thedest1/public_html/rhemahousing.co.uk/dr/modules/ckeditor/includes/ckeditor.page.inc on line 113

I tried adding a php.ini file to my /drupal folder. The file had the contents:
php_value memory_limit = "128M"

this resulted in a different error:
Fatal error: Class 'PDO' not found in .... /includes/database/database.inc on line 184

I have now placed the following code in a php.ini file in my drupal directory. This has solved the problem. I don't understand why, but I'm happy!

php_value memory_limit = "128M"
safe_mode = off
session.cache_limiter = nocache
open_basedir = none
extension = pdo.so
extension = pdo_mysql.so

I hope this helps anyone else with a similar problem.

I had the same situation and tried everything listed here, and it still wouldn't work.
Then I realized that I must have set extension_dir some time in the past. I just commented it out and it worked (just let it use the default value).
HTH.

My old php.ini file was rather full of code scratchouts. No idea why it suddenly stopped working. At the suggestion of the GreenGeeks tech support, I renamed it and created a new, blank php.ini file in my public_html directory and added the following to it:

extension=mcrypt.so
short_open_tag = on
extension=pdo.so
extension=pdo_mysql.so
extension=pdo_sqlite.so
extension_dir = "/usr/local/lib/php/extensions/no-debug-non-zts-20060613"
zend_extension="/usr/local/IonCube/ioncube_loader_lin_5.2.so"

Also had to make sure the following line was in .htaccess:
SetEnv PHPRC /home/cPanelUser/public_html/php.ini
Note: Make sure to replace 'cPanelUser' with the actual username for your account.

Thanksssssssssssssssssssssss you.

One of my website was down for almost 6 month due to this error and I couldn't able to solve it. Now it start working again after I add this line
extension=pdo.so
extension=pdo_sqlite.so
extension=sqlite.so
extension=pdo_mysql.so

Best,

This worked for me... thanks! I had never encountered this issue with previous D7 installs. My php.ini file only contained a line to deal with register_globals and it was causing the PDO error.

I had a working copy of the latest drupal 7.

I only encountered this error yesterday and had not added anything to the system.

Prior to this (a week ago) I had been adding modules but had no errors.

I changed the setup based on the following post: I am running PHP 5.4

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I've been having some issues with Drupal 7 since installation, namely enabling Clean URL's, some Views errors, etc. I remembered during the installation reading that PHP 5.2.5 was the minimum requirement for installation. I wasn't sure which version of PHP my server was running, I created a new php file called phpinfo.php with the following code:
phpinfo();
Turns out I was running 5.2.15. Not being up to date on the latest versions, I assumed 5.2.15 was lesser than 5.2.5 (I found out later that I assumed incorrectly). Anyway, my host was running both 5.2.12 and 5.3.3, so I installed 5.3.3 by adding this to my .htaccess file : Action application/x-hg-php53 /cgi-sys/php53
AddType application/x-hg-php53 .php
I ran phpinfo.php again, and saw PHP 5.3.3 successfully enabled. Problem is, when I went back to my site, I got the misleading "Fatal error: Class 'PDO' not found in /home/public_html/includes/database/database.inc on line 185" After a lot digging and going back-and-forth with my host, and realizing PDO was installed and enabled, and on my php.ini file these two line were already uncommented: extension=pdo.so
extension=pdo_mysql.so
I even tried running the update.php script, but got this: "PDO is required! Drupal 7 requires PHP 5.2.4 or higher with the PHP Data Objects (PDO) extension enabled. See the system requirements page for more information." I found lots of info on http://drupal.org/requirements and http://drupal.org/requirements/pdo, but neither seemed to fix my specific issue. Finally, I found this page http://drupal.org/node/887288 after searching for answers to the error from the update script. While it didn't clearly explain (to me) what was happening in my instance, it did get me to try a different database connection array as indicated in the thread. This ended up WORKING for me with Drupal 7 and PHP 5.3.3:
With PHP 5.2.15 the database connection array performed well when formatted as: $databases = array (
'default' =>
array (
'default' =>
array (
'database' => 'db_name',
'username' => 'db_username',
'password' => 'passwd',
'host' => 'localhost',
'port' => '',
'driver' => 'mysql',
'prefix' => '',
),
),
);
However when upgrading to PHP 5.3.3 the following format is required: $databases['default']['default'] = array(
'driver' => 'mysql',
'database' => 'db_name',
'username' => 'db_username',
'password' => 'passwd',
'host' => 'localhost',
'prefix' => '',
);

Hi,

This happened out of the blue for me - I had made no changes
Commenting out extension_dir in the php.ini sorted it

;extension_dir = "/usr/local/lib/php/extensions/no-debug-non-zts-20060613"

Thanks again