I want to have a different 5.x version of php.
If you're running php 5.2 in either cli or cgi (suphp), and would like 5.3 instead, you can do so with the following commands:
cd /usr/local/directadmin/custombuild ./build set php5_ver 5.3 ./build update ./build php n ./build rewrite_confs
Note that there are changes between these versions and not all scripts will be 100% compatible. See the migration instructions for information on what has changed and if any other actions are required on your part.
If you're looking to change php versions in CustomBuild 2.0, say from php 5.5 to php 5.3, you'd type:
cd /usr/local/directadmin/custombuild ./build set php1_release 5.3 ./build update ./build php n ./build rewrite_confs
CustomBuild 2.0 only supports php 5.3 and higher.