Why install php Software Collections?
Because they are designed to work with your server.
Because the contrib makes it easy when you don't really know what you are doing, and it works with SME so if you have issues we can help.
Most of this has already been explained a thousand times already.
I already have several versions of php installed following certain controls that I use.
In which case unless you give us a lot more information you are on your own.
We have no idea what you have installed or how.
The recommended method of adding newer versions of PHP is via the conteib and Software Collections. I really suggest you use them. I suggest you install/use PHP 7.2 or 7.3 globally.
We don't have the time to sit down and tell you how to install your custom PHP in a given location.
(Note phpinfo is just a php function. It will report what it see from wherever it is run.)
Versions
I have explained already. The installed version 5.3.x is supported by RH until RHEL6 is EOL.
Currently the lowest SCL version of PHP that is normally supported is 7.2
Do not use 5.4/5.6/7.0/7.1
https://www.php.net/supported-versions