The problem described in this KB article has been completely fixed since Parallels Plesk Panel 11.5 (see release notes).
When trying to reconfigure the Apache web server, the following error is displayed:
# /usr/local/psa/admin/sbin/httpdmng --reconfigure-all PHP Fatal error: Class name must be a valid object or a string in /usr/local/psa/admin/plib/Template/Scheme/Webserver.php on line 62
The issue is caused by a database inconsistency:
mysql> select id,name from Configurations where name=''; +-------+------+ | id | name | +-------+------+ | 35075 | | | 35131 | | +-------+------+ 2 rows in set (0.01 sec)` There should be no entries with name=''. The reason these entries are appearing in the database is still under investigation.
The issue will be fixed in a future update for which a new Knowledgebase article will be created. You may subscribe for new articles on Parallels Plesk Panel product if you wish to receive notifications about their creation.
As a workaround you may remove the incorrect entries from the psa database:
#MYSQL_PWD=`cat /etc/psa/.psa.shadow` mysql -uadmin psa ... mysql> delete from Configurations where name='';