after : install openssl first https://www.taxze.com/update-openssl-debian-directadmin/
..and update CustomBuild 2.0 for upgrade php5.5.xx to php7.2.xx on Debian6 & DirectAdmin
cd /usr/local/directadmin
mv custombuild custombuild_1.x
wget -O custombuild.tar.gz http://files.directadmin.com/services/custombuild/2.0/custombuild.tar.gz
tar xvzf custombuild.tar.gz
cd custombuild
./build options
./build set_fastest
./build update_script
./build update_da
./build set php1_release 7.2
./build set php1_mode mod_php
./build update
./build versions
apt-get install -y --force-yes libexpat1 libexpat1-dev libdb4.8-dev libperl-dev
./build apache
./build php n
httpd -v
php -v
reboot
cd /usr/local/directadmin/custombuild
./build rewrite_confs
./build all d
./build rewrite_confs
reboot
cd /usr/local/directadmin/custombuild
./build set opcache yes
./build set mod_ruid2 yes
./build set ioncube yes
./build mod_ruid2
./build ioncubevim /etc/httpd/conf/extra/httpd-info.conf
<Location /server-status>
SetHandler server-status
# Require host .example.com
# Require ip 127
</Location>
ExtendedStatus On
/etc/init.d/httpd restart
reboot