A recent update to php from the Atomic repository is causing issues for some servers and plesk users in general.
Typical symptoms will be :
Starting httpd: Syntax error on line 31 of /etc/httpd/conf.d/php.conf:
Invalid command ‘php_value’, perhaps misspelled or defined by a module not included in the server configuration
and various 501 errors..
Switching the php hander from Apache module to fastcgi will correct some of the issues but you will still get errors if you have php-flags in your .htaccess files.
The reason is in php.conf file provided in 5.3.26 RPM. To fix add these to the top of the file /etc/httpd/conf.d/php.conf