APC is a PHP accelerator extension that can be installed using PECL.  PECL comes with the php-pear package, and must be installed

yum install php-pear

install APC dependencies so that PECL can build APC:

yum install php-devel httpd-devel

yum groupinstall ‘Development Tools’

yum groupinstall ‘Development Libraries’

Now that if all dependencies are installed, you can install APC php accelerator:

pecl install apc

now, you should add “extension=apc.so” to php.ini or create apc.ini file in /etc/php.d/ and add this line

extension=apc.so

now, restart httpd/apache:

/etc/init.d/httpd restart