PHP 5.5 and OpCache for Moodle / Moodle 2.7 on RHEL / CentOS 5

The Problem

On a recent consulting engagement, I was tasked with helping a school eliminate a severe performance issue on its Moode site. I determined the primary solution was to add a PHP accelerator such as APC or OPCache.

Red Hat still supports RHEL 5 for security updates, but the default PHP installation is rapidly becoming unusable for current versions of Moodle. The server's administrators had manually upgraded from the PHP 5.1 version included by Red Hat to a third party PHP 5.3 build. While this allowed them to install a newer version of Moodle, it also ruined the sites performance. The third party build didn't include a PHP accelerator. Because the site was in active use there wasn't enough time to upgrade the entire operating system.

After discusion, with the client, we decided the best option forward was to upgrade to PHP 5.5 and use OPCache for PHP acceleration. This had the additional benefit of making the server ready for Moodle 2.7 and beyond. Here is how we did it.

The solution

We determined we could get a high quality PHP 5.5 build from the Remi repository (http://rpms.famillecollet.com/) that would continue to receive security updates. OPCache is included with PHP 5.5 and beyond.

Setup Remi repository (from cli)

wget http://download.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm

rpm -ivh epel-release-5-4.noarch.rpm

wget http://rpms.famillecollet.com/enterprise/remi-release-5.rpm

rpm -Uvh remi-release-5*.rpm

See http://linuxdrops.com/how-to-add-epel-and-remi-repository-to-centos/

Remove old PHP (from cli)

yum remove php php-soap php-intl php-cli php-mbstring php-common php-pdo php-gd php-xml php-ldap php-mysql php-xmlrpc

Install new PHP (from cli)

yum --enablerepo=remi,remi-php55 install php httpd php-soap php-intl php-cli php-mbstring php-common php-pdo php-gd php-xml php-ldap php-mysql php-xmlrpc php-opcache

See http://www.if-not-true-then-false.com/2010/install-apache-php-on-fedora-centos-red-hat-rhel/

OpCache Configuration

See the following Moodle docs page for Moodle specific OPCache settings http://docs.moodle.org/26/en/OPcache

Risks

Some risks to consider before upgrading

Upgrading PHP can break older PHP applications

Make sure that your version of Moodle will work with a new PHP including all third party plugins. Also be sure any other PHP web applications are your server support the new version.

The new install may fail

There is also a chance that if you do something wrong in the repository setup or have an unusual configuration that you won't be able to successfully install the new version after removing your old PHP, so plan accordingly!

Missing PHP libraries

Each PHP build is different, not every build includes files for every library. Make sure the library you need are in the new version.