You just install mod_suphp with yum install mod_suphp.
After this, /etc/httpd/conf.d/mod_suphp.conf (important this line LoadModule suphp_module modules/mod_suphp.so, rest can be uncommented);
Then edit /etc/suphp.conf
umask=0022
[handlers]
;Handler for php-scripts
php5-script=php:/usr/bin/php-cgi
The major things come with: httpd.include of each domain need to add, before < /VirtualHost >, the line Include /var/www/vhosts/domain.com/conf/vhost.conf
Then create vhost.conf. (We suggest to use for this Power Toys, this will suggest exacctly what you need to do and modify the file for you and enable on new domains by default)
<IfModule mod_suphp.c>
<Directory "/var/www/vhosts/domain.com/httpdocs/">
php_admin_flag engine on
suPHP_Engine On
suPHP_ConfigPath "/var/www/vhosts/domain.com/httpdocs/"
AddHandler php5-script .php
AddHandler x-httpd-php .php5
suPHP_AddHandler php5-script .php
<Files php.ini>
order allow,deny
deny from all
</Files>
php_value open_basedir "/tmp/"
php_value upload_tmp_dir "/var/www/vhosts/domain.com/httpdocs/tmp/"
</Directory>
</IfModule>
As you see, you can have your own php.ini file in httpdocs directory.