MySQL doe not come with Panther; you will have to get it from the link which Jaey referred to you in the previous post.
By default, PHP is disabled in Panther, you will have to enable it by uncommenting (sp?) the appropriate lines in the httpd.conf file in the /etc/httpd/ (default for Apache on OS X) folder. A step-by-step guide can be found
here.
Once both of these are up and running (and given that you have restarted Apache after updating it's configuration file). All you need to do is put the PHP files in the "sites" folder that is under your user name. Don't put any files in the /Library/WebServer/Documents --
Now you can view to your PHP site from your browser using the following url
http://localhost/~username (where the "~username" is your user name)