درود.
مشکل مشابهی برای ما هم بوجود اومده بود (ارور 500):
[22-Feb-2016 12:00:01 Asia/Tehran] PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions/no-debug-non-zts-20090626/suhosin.so' - /usr/lib/php/extensions/no-debug-non-zts-20090626/suhosin.so: cannot open shared object file: No such file or directory in Unknown on line 0[22-Feb-2016 12:00:01 Asia/Tehran] PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions/no-debug-non-zts-20090626/apc.so' - /usr/lib/php/extensions/no-debug-non-zts-20090626/apc.so: cannot open shared object file: No such file or directory in Unknown on line 0
[22-Feb-2016 12:00:01 Asia/Tehran] PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions/no-debug-non-zts-20090626/memcache.so' - /usr/lib/php/extensions/no-debug-non-zts-20090626/memcache.so: cannot open shared object file: No such file or directory in Unknown on line 0
[22-Feb-2016 12:00:01 Asia/Tehran] PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions/no-debug-non-zts-20090626/ixed.5.3.lin' - /usr/lib/php/extensions/no-debug-non-zts-20090626/ixed.5.3.lin: cannot open shared object file: No such file or directory in Unknown on line 0
مربوط به ناسازگاری ورژن پی اچ پی بود... که با تغییر اون به 5.6 برای whmcs ورژن 6.1.2 حل شد.