Run PHP with CGI and Apache on Ubuntu 12.04 LTS (Precise Pangolin)

In instances where running the mod_php module to run PHP scripts on Apache is not sufficient, PHP can be run as a CGI binary. Combined with the itk multi-processing module (MPM), PHP scripts can be run as user processes in a per-virtual host setup. This guide will walk users through the process of setting up Apache and PHP CGI.

Before You Begin

1. If you have not already done so, create a Linode account and Compute Instance. See our Getting Started with Linode and Creating a Compute Instance guides.

2. Follow our Setting Up and Securing a Compute Instance guide to update your system and configure your hostname. You may also wish to set the timezone, create a limited user account, and harden SSH access.

   To check your hostname run:

   hostname
   hostname -f
   

   The first command should show your short hostname, and the second should show your fully qualified domain name (FQDN) if you have one assigned.

Installing Apache and PHP

1. If you have not already installed the Apache HTTP server, do so:

   sudo apt-get install apache2
   

   You can now configure virtual hosting in accordance with the needs of your server.

2. Install the PHP CGI binaries:

   sudo apt-get install php5-cgi
   

   When this process completes, we can configure Apache to hand PHP scripts to the CGI process for rendering these scripts.

Configure Apache for PHP CGI

In order to set up Apache to use PHP-CGI on Ubuntu systems, you must enable the mod_actions module. Issue the following command:

sudo a2enmod actions

The required directives can be set anywhere in Apache’s configuration tree . We recommend creating the php-cgi.conf file in Apache’s conf.d/ directory and setting these variables there. For Ubuntu systems, this is located at /etc/apache2/conf.d/. You may also choose to place these settings in your /etc/apache2/httpd.conf file. Regardless of their location, the relevant settings are:

File: Apache Configuration Block

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ScriptAlias /local-bin /usr/bin AddHandler application/x-httpd-php5 php Action application/x-httpd-php5 /local-bin/php-cgi

In this example, the path to the php-cgi binary is /usr/bin/php-cgi. All files with the php extension will be handed to the PHP CGI binary.

You may also choose to put these configuration directives within a virtual hosting block. If you do not have mod_php enabled or installed, you can use this to selectively enable PHP for certain virtual hosts. Furthermore, if your deployment requires multiple versions of PHP, you can specify virtual host specific handlers by specifying paths to various versions of php-cgi.

The configuration file for the CGI executable of PHP is located at /etc/php5/cgi/php.ini. You can modify this file to suit the needs of your deployment.

File: /etc/php5/cgi/php.ini

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error_reporting = E_COMPILE_ERROR|E_RECOVERABLE_ERROR|E_ERROR|E_CORE_ERROR display_errors = Off log_errors = On error_log = /var/log/php.log max_execution_time = 30 memory_limit = 64M register_globals = Off

If you need support for MySQL in PHP, then you must install the php5-mysql package with the following command:

sudo apt-get install php5-mysql

When php-cgi is configured, you can now safely enable the itk multi-processing module for Apache. The installation process for itk will restart the Apache process. If you choose to use PHP CGI with the default or existing MPM, then restart Apache by issuing the following command:

sudo service apache2 restart

Enabling the “itk” MPM

The default Apache configuration uses a multi-processing module called worker which uses a threaded approach to efficiently handle HTTP requests. An alternative MPM is prefork which does not use threads and is compatible with non-thread-safe libraries. Both the worker and prefork modules require that all requests be handled by a process running under a user with particular permissions. On Ubuntu systems, Apache processes run under the www-data user.

This may not be ideal if you have multiple users running publicly accessible scripts on your server. In some of these cases, it is prudent to isolate virtual hosts under specific user accounts using an alternative MPM, known as itk or mpm-itk. Functionally, mpm-itk is quite similar to prefork; however, itk can process requests for each virtual host or each site under a specified user account. This is useful in situations where you’re hosting a number of distinct sites and you need to isolate sites on the basis of user privileges.

1. Install the mpm-itk module:

   sudo apt-get install apache2-mpm-itk
   

2. In the <VirtualHost > entries for your sites (the site-specific files in /etc/apache2/sites-avalible/) add the following sub-block:

   File: Apache Virtual Hosting Configuration Block

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   <IfModule mpm_itk_module> AssignUserId webeditor webgroup </IfModule>

In this example, webeditor is the name of the user of the specific site in question, and webgroup is the name of the user group that “owns” the web server related files and processes for this host. Remember that you must create the user accounts and groups using the useradd command. Consider our documentation of user groups and permissions for more information about creating the necessary users and groups.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

• The PHP Homepage
• Apache 2.2 CGI documentation