Assigning Template Variable from a Post?

Hey all, I looked around briefly but couldn’t find a lot of information that would help me out. I’m building a custom content-single.php, and I’d like for it to be a template that uses php variables that will eventually be called from a SQL database. For now though, I’d like to assign the variables in the_content() if possible.

I have the ‘PHP Exec’ plugin installed, which allows php to be inserted in posts between <phpcode> tags, and it seems to be working fine.

As a test, I initialized a test variable on the actual content-single.php above the call for the_content() with

<php
     $address = 'default';
?>

then in the actual wordpress content editor, i’ve written

<phpcode>
     <?php
          $address = 'success';
     ?>
</phpcode>

back to content-single.php, after the template calls the_content(), I’ve got

<?php
     echo $address;
?>

which is returning “default” on the actual page.

So with a little bit of research, it looks like a problem of the variable’s scope because I’m assigning it within a function. Do I use globals here? I’m not sure exactly how to proceed, any advice would be appreciated.