And this is what I get in the error log file:
[Wed Nov 27 09:11:18 2013] [error] [client 173.54.16.212] PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'wp_heartbeat_settings' not found or invalid function name in /var/www/vhosts/santiapps.com/httpdocs/wp-includes/plugin.php on line 199, referer: https://santiapps.com/
[Wed Nov 27 09:11:18 2013] [error] [client 173.54.16.212] PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'wp_heartbeat_settings' not found or invalid function name in /var/www/vhosts/santiapps.com/httpdocs/wp-includes/plugin.php on line 199, referer: https://santiapps.com/
[Wed Nov 27 09:11:49 2013] [error] [client 66.117.9.84] PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'wp_authenticate_spam_check' not found or invalid function name in /var/www/vhosts/santiapps.com/httpdocs/wp-includes/plugin.php on line 199, referer: https://santiapps.com/wp-login.php
[Wed Nov 27 09:11:50 2013] [error] [client 66.117.9.84] PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'wp_authenticate_spam_check' not found or invalid function name in /var/www/vhosts/santiapps.com/httpdocs/wp-includes/plugin.php on line 199, referer: https://santiapps.com/wp-login.php
[Wed Nov 27 09:11:50 2013] [error] [client 66.117.9.84] script '/var/www/vhosts/santiapps.com/httpdocs/wp-index.php' not found or unable to stat, referer: https://santiapps.com/wp-index.php
[Wed Nov 27 09:12:00 2013] [error] [client 192.99.6.118] File does not exist: /var/www/vhosts/santiapps.com/httpdocs/phpbb3, referer: https://santiapps.com/phpbb3/posting.php?
mode=post&f=2+%5BPLM=0%5D+GET+https://santiapps.com/phpbb3/index.php?sid=7ed098d0cf3156266e50363e3075e647+%5B0,8560,15094%5D+-%3E+%5BL%5D+POST+https://santiapps.com/phpbb3/ucp.php?mode=login+%5B0,0,8086%5D+-%3E+%5BL%5D+GET+https://santiapps.com/phpbb3/index.php?&sid=afbeb848e545fa9f9c89fc070e98a49b+%5B0,0,15143%5D+-%3E+%5BN%5D+GET+https://santiapps.com/phpbb3/viewforum.php?f=1+%5B0,0,9605%5D+-%3E+%5BN%5D+GET+https://santiapps.com/phpbb3/viewforum.php?f=2+%5B0,0,16721%5D+-%3E+%5BN%5D+GET+https://santiapps.com/phpbb3/posting.php?mode=post&f=2+%5B0,21395,21802%5D+-%3E+%5BN%5D+POST+https://santiapps.com/phpbb3/posting.php?mode=post&f=2&sid=afbeb848e545fa9f9c89fc070e98a49b+%5B0,0,7255%5D+-%3E+%5BN%5D+GET+https://santiapps.com/phpbb3/posting.php?mode=post&f=2+%5B0,0,21802%5D+-%3E+%5BN%5D+GET+https://santiapps.com/phpbb3/posting.php?mode=post&f=2+%5B0,0,21802%5D+-%3E+%5BN%5D+GET+https://santiapps.com/phpbb3/index.php+%5B7111,0,15143%5D
[Wed Nov 27 09:12:01 2013] [error] [client 192.99.6.118] File does not exist: /var/www/vhosts/santiapps.com/httpdocs/phpbb3, referer: https://santiapps.com/phpbb3/posting.php?mode=post&f=2+%5Bplm=0%5D+get+https://santiapps.com/phpbb3/index.php?sid=7ed098d0cf3156266e50363e3075e647+%5B0,8560,15094%5D+-%3E+%5Bl%5D+post+https://santiapps.com/phpbb3/ucp.php?mode=login+%5B0,0,8086%5D+-%3E+%5Bl%5D+get+https://santiapps.com/phpbb3/index.php?&sid=afbeb848e545fa9f9c89fc070e98a49b+%5B0,0,15143%5D+-%3E+%5Bn%5D+get+https://santiapps.com/phpbb3/viewforum.php?f=1+%5B0,0,9605%5D+-%3E+%5Bn%5D+get+https://santiapps.com/phpbb3/viewforum.php?f=2+%5B0,0,16721%5D+-%3E+%5Bn%5D+get+https://santiapps.com/phpbb3/posting.php?mode=post&f=2+%5B0,21395,21802%5D+-%3E+%5Bn%5D+post+https://santiapps.com/phpbb3/posting.php?mode=post&f=2&sid=afbeb848e545fa9f9c89fc070e98a49b+%5B0,0,7255%5D+-%3E+%5Bn%5D+get+https://santiapps.com/phpbb3/posting.php?mode=post&f=2+%5B0,0,21802%5D+-%3E+%5Bn%5D+get+https://santiapps.com/phpbb3/posting.php?mode=post&f=2+%5B0,0,21802%5D+-%3E+%5Bn%5D+get+https://santiapps.com/phpbb3/index.php+%5B7111,0,15143%5D
[Wed Nov 27 09:12:01 2013] [error] [client 192.99.6.118] PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'wp_heartbeat_settings' not found or invalid function name in /var/www/vhosts/santiapps.com/httpdocs/wp-includes/plugin.php on line 199, referer: https://forum.santiapps.com/
[Wed Nov 27 09:12:03 2013] [error] [client 192.99.6.118] script '/var/www/vhosts/santiapps.com/httpdocs/wp-content/uploads/2013/11/index.php' not found or unable to stat, referer: https://santiapps.com/index.php
[Wed Nov 27 09:12:03 2013] [error] [client 192.99.6.118] File does not exist: /var/www/vhosts/santiapps.com/httpdocs/uploads, referer: https://santiapps.com/uploads/2013/11/index.php
[Wed Nov 27 09:12:03 2013] [error] [client 192.99.6.118] script '/var/www/vhosts/santiapps.com/httpdocs/wp-content/uploads/2013/11/index.php' not found or unable to stat, referer: https://santiapps.com/index.php
[Wed Nov 27 09:12:03 2013] [error] [client 192.99.6.118] File does not exist: /var/www/vhosts/santiapps.com/httpdocs/uploads, referer: https://santiapps.com/uploads/2013/11/index.php
[Wed Nov 27 09:12:04 2013] [error] [client 192.99.6.118] script '/var/www/vhosts/santiapps.com/httpdocs/wp-content/uploads/2013/11/index.php' not found or unable to stat, referer: https://santiapps.com/index.php
[Wed Nov 27 09:12:04 2013] [error] [client 192.99.6.118] File does not exist: /var/www/vhosts/santiapps.com/httpdocs/uploads, referer: https://santiapps.com/uploads/2013/11/index.php
[Wed Nov 27 09:12:08 2013] [error] [client 203.150.3.59] PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'wp_authenticate_spam_check' not found or invalid function name in /var/www/vhosts/santiapps.com/httpdocs/wp-includes/plugin.php on line 199, referer: https://santiapps.com/wp-login.php
[Moderator Note: Please post log files between backticks or use the code button.]