phpinfo still showing php version 5.5 after upgrade

Which version of Centmin mod? For php 7.2 you want to be on 123.09beta01 first as 123.08stable doesn't really fully support PHP greater than 7.0.

Every centmin.sh menu option has a full server log created with time stamped file name at /root/centminlogs. You can check that specific error log for clues or copy and paste log contents and post to pastebin.com or gist.github.com for sharing.

To troubleshoot, you need to check the the php upgrade logs at /root/centminlogs and instructions under Sharing logs and errors heading for using Pastebin.com or Gists to share a sanitised version of the contents of the nginx_upgrade and php_upgrade logs. You can see full details at How to troubleshoot Centmin Mod initial install issues

if you type this command it lists all logs in date ascending order so latest log at bottom

Code (Text):

ls -lArt /root/centminlogs

so copy the entire contents of latest php_upgrade log to gist.github.com or pastebin.com

you can use grep to filter the logs, i.e. look for nginx_upgrade or php in log name

Code (Text):

ls -lahrt /root/centminlogs/ | egrep 'nginx_upgrade|php_upgrade'

Code (Text):

ls -lahrt /root/centminlogs/ | egrep 'nginx_upgrade|php_upgrade'
-rw-r--r--  1 root root  2.6M Oct  3 03:48 centminmod_1.2.3-eva2000.09.001_031016-034409_php_upgrade.log
-rw-r--r--  1 root root  664K Oct 12 09:24 centminmod_1.2.3-eva2000.09.001_121016-092406_nginx_upgrade.log

So the last php upgrade log was named centminmod_1.2.3-eva2000.09.001_031016-034409_php_upgrade.log and located at /root/centminlogs/centminmod_1.2.3-eva2000.09.001_031016-034409_php_upgrade.log
then use cat command to output the contents of that log.

clear your ssh window buffer/screen and type

Code (Text):

cat /root/centminlogs/centminmod_1.2.3-eva2000.09.001_031016-034409_php_upgrade.log

then select and copy and paste output to pastebin.com or gist.github.com file to share. If your SSH client's scroll buffer isn't large enough using cat might not output the entire log file contents, so you may need to download the log and use local text editor to open and copy and paste.

so only need content of a specific log, in this case most recent php_upgrade.log logs

Upgrading Centmin Mod Code to Latest Version

Upgrading Centmin Mod involves 2 parts.

1. Upgrading the actual Centmin Mod code outlined at Upgrade Centmin Mod - CentminMod.com LEMP Nginx web stack for CentOS This is heart of Centmin Mod where the code is the engine that runs centmin.sh shell based menu and all the automation you're accustomed to.
2. Upgrade software that Centmin Mod installed or manages. For this part following outline at Upgrade - How to upgrade Centmin Mod | Centmin Mod Community

So essentially, you can upgrade from .07 to .08 in place, but not everything is upgraded as some things like server initial environment setup isn't changed i.e. how swap, tmp setup and allocation are created etc. The main parts from part 2 above are what in place upgrades do i.e. Nginx and PHP-FPM compilation and config/settings parameters and MariaDB version from 5.5 to 10.0.x. If you want the full environment changed including tmp and swap setup to .08's configuration, then you would need a fresh OS install and fresh .08 initial install. You can think of it like upgrading Windows 7 to Windows 8. An in place upgrade will upgrade code but won't change your computer environment from when you installed Windows 7 i.e. disk configuration and partition sizes won't change from when you initially installed Windows 7. Only way to change that would be fresh Windows 8 install.