Installation guide

We have taken great care to ensure that the SDK will perform well in an environment that utilizes an opcode cache.

Note

PHP 5.5 comes with an opcode cache that is installed and enabled by default:

http://php.net/manual/en/book.opcache.php

If you are using PHP 5.5, then you may skip the remainder of this section.

APC

If you are not able to run PHP 5.5, then we recommend using APC as an opcode cache.

Installing on Amazon Linux

When using Amazon Linux, you can install APC using one of the following commands depending on if you are using

PHP 5.3 or PHP 5.4.

# For PHP 5.4

yum install php54-pecl-apc

# For PHP 5.3

yum install php-pecl-apc

Modifying APC settings

APC configuration settings can be set and configured in the apc.ini file of most systems. You can find more

information about configuring APC in the PHP.net APC documentation.

The APC configuration file is located at /etc/php.d/apc.ini on Amazon Linux.

# You can only modify the file as sudo

sudo vim /etc/php.d/apc.ini

apc.shm_size=128M

It is recommended that you set the apc.shm_size setting to be 128M or higher. You should investigate what the right

value will be for your application. The ideal value will depend on how many files your application includes, what other

frameworks are used by your application, and if you are caching data in the APC user cache.

You can run the following command on Amazon Linux to set apc.shm_size to 128M:

sed -i "s/apc.shm_size=.*/apc.shm_size=128M/g" /etc/php.d/apc.ini

apc.stat=0

The SDK adheres to PSR-0 and relies heavily on class autoloading. When apc.stat=1, APC will perform a stat on

each cached entry to ensure that the file has not been updated since it was cache in APC. This incurs a system call

for every autoloaded class required by a PHP script (you can see this for yourself by running strace on your

application).

You can tell APC to not stat each cached file by setting apc.stat=0 in you apc.ini file. This change will generally

improve the overall performance of APC, but it will require you to explicitly clear the APC cache when a cached file

should be updated. This can be accomplished with Apache by issuing a hard or graceful restart. This restart step

could be added as part of the deployment process of your application.

You can run the following command on Amazon Linux to set apc.stat to 0:

sed -i "s/apc.stat=1/apc.stat=0/g" /etc/php.d/apc.ini

Performance Guide