PHP works with Apache and suEXEC like this:
(Assuming that suEXEC ist allready installed and working)
Install PHP as CGI binary (e.g. in /usr/local/bin/php)
(compile with --enable-force-cgi-redirect)
Create a Link inside cgi-bin directory to make php-cgi accessable:
cd /usr/local/apache/cgi-bin
ln /usr/local/bin/php php
Edit your httpd.conf file:
AddHandler php4-script .php
Action php4-script /cgi-bin/php
<VirtualHost 123.456.789.0:80>
User exampleuser
Group examplegroup
...
</VirtualHost>
Restart Apache
PHP-scripts are now called under the user-id of exampleuser and group-id of examplegroup.