I run several different wordpress sites and need to start upgrading them each to php5. For this installation, I am going to walk through the steps to make a clean install and upgrade to php5. I will put in italics the steps to use if you are wanting to keep your old installation of wordpress but just upgrade it to php5. So here is a quick guide to the way that worked for me:

Step #1 – Back up everything! WordPress.org has a great sheet on how to backup your wordpress installation. Essentially there are two items you have to back up: 1) Your wordpress installation (what you access via ftp) and 2) your wordpress Database (what you may have accessed with MySQL or phpmyadmin. For backing up my wordpress installation, I just open up my mac ftp client (I love Transmit) and then copy over (from the ftp server to my local hard drive) my entire wordpress folder. Then I use wp-db-Backup (which is a plugin you can add inside your wordpress dashboard) to backup my wordpress database.

Step #2 – Delete WordPress Installation. Once you have triple-checked to make sure your installation is all backed-up, then delete the wordpress installation on the FTP site.

Step #3 – Upload a fresh install of wordpress. Download the latest version of wordpress and upload it to your ftp site. Alternatively, I believe you can just re-upload the back up of your installation since it will have all of your themes and plugins already configured. While you are waiting on the ftp upload to finish, you can go ahead and…

Step #4 – Create a new database. Log on to your hosting account and create a new database in MySQL. (Make sure it is PHP 5!) Once it has been created, copy all of the necessarily information into your wp-config file (regardless of if it is a new install or the original files for the wordpress install). If you are unsure how to do this, check out the instruction for setting up your wp-config file on wordpress.org.

Step #5 – “Install” your new WordPress Installation. Once all of you files have been uploaded and you have modified your wp-config.php file, then open up a web browser window & go to root/wordpress/wp-admin/install.php and let er rip!  If you are upgrading a previous wordpress installation and re-uploaded your wordpress installation, then go to root/wordpress/wp-admin/upgrade.php.

Step #6 – Restore your MySQL database. Open up your phpmyadmin page for the new database you created and then import the php 4.0 mysql backup you made earlier. If you have issues, just open up the phpmyadmin page for the old database and re-export it using these guidlines.

Step #7 – Clean up. At this point everything should be back up and running. If you did the clean install, you may need to reinstall some themes and plugins (I highly recommend the wp-db-Backup to keep regular backups of your files). Once you are sure everything is back up and running correctly, you can go ahead and delete the original php 4.0 MySQL database.