Actually, even if it were in a text file, it likely wouldn't get read from the hard drive with every request, since file caching should make sure that it stays in memory.
but if you really want to make something common to apache, look at SSI, server side includes, or writing your own module (which is MUCH easier than you might think.)
The other way is to use an include file, like so:
include ("vars");
then write all the vars you want into the include file so it looks like this:
<?php
$var1=value1;
$var2="string2";
?>
