How to Install the PHP APC Extension
APC is an opcode cache that allows PHP to save and reuse the intermediate code generated from PHP source code as a speed optimization.
To enable APC's separate object caching functionality in PHP 5.5+, do not install APC. Instead, install the APCu extension.
To install this extension, SSH into your server as root and run the following command:
sudo apt-get install gcc make autoconf libc-dev pkg-config sudo pecl5.4-sp install apc
Press Enter when asked configuration questions unless you know you want to change any of the defaults.
Once installed, create a configuration file for the extension and restart PHP by running the following commands as root:
sudo bash -c "echo extension=apc.so > /etc/php5.4-sp/conf.d/apc.ini" sudo service php5.4-fpm-sp restart
Debugging Compilation Errors
The following error means you tried to build APC for PHP 5.5 or PHP 5.6. PHP 5.5 and 5.6 include opcode caching by default. APC does not work with PHP 5.5+.
/tmp/pear/temp/APC/apc_compile.c:2417:9: error: 'zend_trait_precedence' has no member named 'function' make: *** [apc_compile.lo] Error 1 ERROR: `make' failed