scope issues

MySymfonyConroller.php

<?php

/***************
 *
 * My Wordpress plugin
 *
 *********************/

$myvar = "Hello";
function show_my_var(){
  global $myvar;
  echo "myvar = ".$myvar;
}

show_my_var();

/***************
 *
 * My Symfony controller
 *
 *********************/

class MyController {
	public function myAction(){
		include 'my-wordpress-plugin.php';
	}
}
$c = new MyController();
$c->myAction();