How to Enable PHP Opcache on PHP 5.5 and Ubuntu 14.04

With the release of Ubuntu 14.04 and the proliferation of PHP 5.5, there is going to be a migration away from Alternative Performance Cache (APC) and toward PHP’s new built-in OPcache.

This is a logical move that seems destined for any interpreted language.  As websites have become more and more complicated with many processes running, opcode caching has become a necessity – fortunately, it’s simple to implement.
The php.net site has a nice page of all the runtime options available, but we will cover the basics here to get you started quickly.
All you need to do to get OPcache set up is to make changes in the php.ini file on your server.

Open php.ini In Your Favorite Text Editor

To get started open your php.ini file.

Apache web-servers

1	/etc/php5/apache2/php.ini

Nginx web-servers with PHP-FPM

1	/etc/php5/fpm/php.ini

Enable the OPcache

To enable the OPcache, change to the following lines — easy enough!

1	;opcache.enable=0

Change to:

1	opcache.enable=1

Note: you have to uncomment this line as well as change the “0″ to “1″.

Modify the Amount of RAM the OPcache Will Use

With OPcache, there is a trade-off between speed and the amount of RAM used. The more RAM you are willing to dedicate to storing opcode, the more opcode that can be stored. There is a diminishing return at some point, because some code will execute rarely, or your code base might not be that big. It is worth playing with this setting to see where you get the best performance-versus-RAM trade-off.  This setting is in megabytes.

1	;opcache.memory_consumption=64

Change to:

1	opcache.memory_consumption=128

Boost the Number of Scripts that Can Be Cached

OPcache has a strange setting that requires you to not only adjust the amount of RAM, but also define the number of scripts that can be cached. You have the option of tuning this parameter for your own application too, especially if you find that your hit rate is not close to 100 percent.

1	;opcache.max_accelerated_files=2000

Change to:

1	opcache.max_accelerated_files=4000

Change the Revalidate Frequency

To make sure that the OPcache notices when you change your PHP code, you can set the revalidate frequency. Basically, this will tell the cache how often to check the timestamp on the files. This is measured in seconds.

1	;opcache_revalidate_freq = 2

Change to:

1	opcache_revalidate_freq = 240

Verify that the PHP OPcache Mod is Enabled

Believe it or not, that converts most of the settings you will need to get started. PHP5 has its own module system (since 5.4), so make sure that OPcache is enabled.

1	sudo php5enmod opcache

Restart PHP and Your Server

You should now be all set to start using PHP 5.5’s OPcache. You just need to restart your server to get it going.

Apache Web-Servers

1	sudo service apache2 restart

Nginx Web-Servers

1	sudo service nginx restart

Conclusion

Well, there you have it. It’s actually amazingly simple to get this up and running. There are a number of options that allow you to monitor your hit rate with OPcache. Here is an open-source solution (OPcache Status) that can be found on GitHub.