Evidently the idea of using that function in the scope you are attempting wasn't considered previously.
To work around the limitation, you could do this:
In ipn_application_top.php around line 88 you have:
Code:
// define general functions used application-wide
require(DIR_WS_FUNCTIONS . 'functions_general.php');
require(DIR_WS_FUNCTIONS . 'html_output.php');
require(DIR_WS_FUNCTIONS . 'functions_email.php');
simply add this on the next line below the call to functions_email:
Code:
require(DIR_WS_FUNCTIONS . 'functions_ezpages.php');