I have several clients asking that I upgrade to php5. I'm currently running php4.4.4 on Redhat Enterprise 3 with Apache version*1.3.37 (Unix) and MySQL4.0.27 Standard. I understand that it will be necessary that I upgrade MySQL to either 4.1 or 5 if I want to upgrade to php5. Is there any advantage to upgrading only to MySQL4.1 rather than MySQL5 in order to avoid problems with current databases? Or, am I likely to face problems with either MySQL 4.1 or 5 when upgrading from 4.0.27? Are there any other upgrades that I'll be required to make in order to upgrade my php to 5.2.x? (e.g., Apache?) I'm mostly concerned with Mailman. I have several clients running Mailman mailing lists. I also have a few clients who have installed one or the other Fantastico scripts. Of course, I'll warn my clients to make backups, and I'll have cPanel do the same, but am I likely to have to deal with problems if I upgrade? If so, what sorts of problems might I face?