Fixing zend_mm_heap corrupted on Centos 5.x

When you do a google search on 'zend_mm_heap corrupted' you will find it's been keeping sysadmins busy for some time. I had it on one of my new production boxes (Centos 5.2) after updating to php 5.2.9, and later after updating apache to 2.2.3. It is not a PHP problem!, it is related to the php extensions in use.

Extension: Memcached
If you use memcached in php as a session handler; first check
* Is memcached started
* Is the serverconfig (in /etc/php.ini or /etc/php.d/memcache.ini) correct?

Not being able to connect to the memcached server will result in zend_mm_heap corrupted


Other extensions
To troubleshoot the problem
* Move all extension configs from the /etc/php.d directory to a safe place
* Add them one by one, restart httpd and reload the page after each add
* This way (isolation) you will find the extension that is causing the problem