You may see below mentioned error after installing APC.

PHP Startup: apc.shm_size now uses M/G suffixes


Now to resolve the issue, you just need to edit the servers php.ini file, default php.ini filel path is /usr/local/lib/php.ini

Edit the file /usr/local/lib/php.ini and search for apc.shm_size, you will see below value:

apc.shm_size="256"


Now just change the value to:

apc.shm_size="256M" Or apc.shm_size="512M" Or apc.shm_size="1G"
After changing the value restart the apache service by below command:

service httpd restart Or /etc/init.d/httpd


That's it! you should not receive such errors any more.