I wasn't planning to upgrade PHP today, but in order to use Symfony 4.0, I had to.
First, I wanted to get all the PHP RPMs
Next, I removed all the PHP 5.5 RPMs:
Then I edited the output file (php) and added a sudo yum install at the beginning of the file
So I could use
There were a few more RPMs I needed, after roaming about the web for a bit, these were the commands that I ran
The recklessly part of this is that I confess I did not check ... anything. My existing Symfony 3.3.10 application comes up and lets me log in. I haven't checked more than that.