If you like to test the PHP of a website, create an "info.php file with this content:
This should also show that Ioncube is installed etc.
So now you need to go into ISPConfig3--->System-->Remote Users add a username and password tick all the boxes that are available
When you are done go to your ssh windows as root and do
It will ask for a username and password. Use the data you added to ISPConfig3 when you create your remore user in the previous step.
Let the script finish and you should be good to go. You can find Softuculous under ISPConfig3-->Tools->Softaculous