Sometimes when PHP is upgraded on the server running Iodine (currently humboldt) the php.ini has to be changed because the path to the extensions changed (since we keep changing where we are getting PHP from). Change the line
extension_dir = "/usr/lib/php5/20050922/"
To contain whatever directory actually exists in /usr/lib/php5/, and is the most recent.
Also, note that the current PHP packages installed are from dotdeb.org, and are not official Debian ones. This is so we can get packages for the mcrypt and imap extensions, in packaged form easily. And, these packages also happen to be running a more recent version of PHP, which is good.