Installing Common PHP Extensions

PHP is a simpler programming language which offers the power of the more complex object orientated languages without some of the more complex data management issues. PHP is commonly used to develop dynamic web content, especially content based upon a database like MySQL. PHP is an on-demand compiled language, where it uses the Apache2 web server to compile the PHP code when the script is run.

In a practical sense, you must have Apache installed to use PHP on your server. If you do not have Apache currently installed, instructions can be found here. Instructions for installing PHP after you have installed Apache can be found here.

The base PHP distribution comes with a lot of the core features, but only core type features. You will often run across situations where you need a PHP Extension or Application Library. PHP extensions are divided between 2 repositories; PECL and PEAR. The difference between the repositories is the type of files each contain. PECL contains C compiled files while PEAR contains special PHP classes. This makes the PECL extensions faster and more powerful than PEAR extensions, however they can have robustness issues since programming in C is much more challenging.

Installing PECL

These instructions assume you have already setup an AWS instance and have an SSH client (like PuTTY) available.

  1. Log in to your instance via the SSH client. Transfer to the root user.
  2. Use PECL to install pecl extension
  3. Press “Y” when it asks if you want to install the extension. Depending on the extension, there may be multiple options you can choose during the installation.
  4. Verify the installation occurred correctly by starting/restarting the httpd service

Summary of command line inputs (example uses pecl_http extension)

  • $ sudo su
  • $ pecl install pecl_http
  • …..
  • $ service httpd restart

Popular PECL extensions

Extension Description PHP-Devel?
pecl_http HTTP request & response processing Y
mailparse Parsing email addresses N

Installing PHP-Devel

Some of the extensions, the PECL ones in particular, require the php-developer package to work properly. If you get an error like “needs php-devel to be installed’ when you attempt to install a package, you will need to install the php-developer package.

These instructions assume you have already setup an AWS instance and have an SSH client (like PuTTY) available.

  1. Log in to your instance via the SSH client. Transfer to the root user.
  2. Use YUM to install PHP-Devel
  3. Press “Y” when it asks if you want to install the extension.
  4. Verify the installation occurred correctly by starting/restarting the httpd service

Summary of command line inputs

  • $ sudo su
  • $ yum install php-devel
  • …..
  • Do you want to install PHP-Devel (Y/N): Y
  • $ service httpd restart

Note about PHP-Devel

When I installed PHP-Devel it changed the ownership and permissions of my session directory. This caused session_start() to fail with a “Permission Denied (13)” error. To fix the error I had to change the ownership back to the Apache user/group that is used when PHP is run on the session directory.

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