Here is the options.conf of one of my servers (it uses CB plugin):
#PHP settings.
#Default version of PHP is always php1_release. Possible values for php1/php2_release: 5.3, 5.4, 5.5, no. php1/php2_mode: mod_php, fastcgi, php-fpm or suphp)
php1_release=5.5
php2_release=no
php1_mode=mod_php...