If you have hosting with Dreamhost or any other host which gives you a shell account, you can install your own custom version of PHP. I needed to compile PHP with GMP support for the OpenID login plugin for WordPress, so I spent the whole day tweaking trying to get everything working. There's a page on Dreamhost's Wiki which has a script, but it still took me hours to get right. I've written a quick guide to help avoid the mistakes which slowed me down.
  1. The first thing you need to do is download Putty and set it up to connect to your host.
  2. We're going to create a few shell scripts to install PHP and all the other packages it requires. It's probably easiest to make your edits in notepad or another text editor, then copy and paste them into Putty by right-clicking. If you just create the files then upload them, there tend to be problems with line breaks and the script doesn't work.
  3. Start by downloading the preparation script and the installation script. Open them with a text edtitor and change the line export DOMAIN="yourdomainhere.com" to match the domain you're installing the CGI script on. This should be the directory the domain is served from. Eg: If your site serves files from /home/someone/xyz.com, use xyz.com. The version information may need updating, because I won't be updating this script.
  4. The first script we need to set up will download the different packages and extract them. Once you're done editing, hit CTRL+A in your text editor, then copy everything to your clipboard. Create a new file by typing nano php_prep.sh at the command prompt.
  5. Paste the contents of your clipboard into the new file by right clicking in Putty, then hit CTRL+O to save the file, then CTRL+X to exit nano.
  6. In *nix you need to make files excutable before you can run them. Do this by typing chmod +x php_prep.sh
  7. Now we need to set up the script which does the installing. Create a new file by typing nano php_inst.sh at the prompt, then copy and paste the contents of your edited php_inst.sh file by right clicking the terminal. Hit CTRL+O, Return, then CTRL+X to save and exit.
  8. Make the file executable by typing chmod +x php_inst.sh
  9. Now that everything's set up, we can run the first script by typing ./php_prep.sh at the prompt. It might take a while but if there are no errors you should eventually see "Done downloading and unpacking prerequisites".
  10. Run the installation script using ./php_inst.sh . This might take a while to complete, so start solitaire or something.
  11. When everything's finished, you should see "INSTALL COMPLETE!" and have a shiny new custom version of PHP installed.
  12. If you don't already have one, create a .htaccess file at the root of your domain. You can do this by typing nano .htaccess. Add the following lines:
    CODE
          Options +ExecCGI
          AddHandler php-cgi .php
          Action php-cgi /cgi-bin/php.cgi
  13. That should be it. If there were no errors, you can test your installation by viewing a PHP file on your site. Hopefully you'll either see no change, but it's possible you'll see a load of errors.

I'm not an expert with Linux, but I'll try to help with any problems people may run in to.

I also posted this article on my blog, which has loads of other technical How-Tos and tutorials.