A keen observation about WA being the most fabulous set of tools in the world. You are a very wise man.
I can explain it.
Just create a file that defines the values that you want to be able to be updated for each application very easily in a config.php file you place somewhere on your site.
Then anywhere you use those values, make sure to include that file on top of the page so that the variables are defined from it and then refer to those variables in the application in place of the hard coded values.