WordPress 3.2 has some significant upgrades.
However, it also pushes the web forward to new versions of key technologies by dropping support for older versions of PHP and MySQL and Internet Explorer. The last one is relatively easy to fix - you can download the lastest version of IE. However, if you're not sure about your PHP and MySQL versions, here's what to do:
1. Check Before You Upgrade
The upgrade process is the same as it always was, but before installing 3.2, or upgrading from an older version, verify that you are using AT LEAST PHP 5.24 and MySQL 5.0. The new version of WP abandons the older versions and moves forward. These versions are not the newest, but they are the oldest acceptable versions. You need these versions or higher.
There are a couple of ways to do this.
If you can't do the upgrade for yourself in the control panel, and the hosting company doesn't allow it, you need to think about switching hosts. WordPress is dropping support for the older versions, and you won't be able to upgrade or install 3.2.
2. Install Health Check
Either download it and install it manually or
3. If you can't use Health Check, to avoid confusion check the chart.
The numbering system for php releases can be confusing. If it were decimals, .4 would be higher than .15, and that throws a lot of people off.. Is 5.2.4 higher or lower than 5.2.15? In your webhost's control panel thery may be a selection process (in a drop-down menu or radio buttons) for changing the level of php version., the only selection may be PHP 5. I've been reading forums and this seems to be a common problem. To make it easy, If the version is not on the list above. It won't work
4. Do a site backup
To get advice on backing up check out this page in the WordPress codex: http://codex.wordpress.org/WordPress_Backups
We've already written a tutorial on doing an automatic site back up http://www.ostraining.com/blog/wordpress/how-to-automatically-backup-wordpress/
5. Go to the admin area
Click "Please update now" and you'll see the message below. Just click on "Update Automatically
6. Click "Update Automatically"
Return to the dashboard and you're done.