pfSense

Sounds risky :) Is that in the currently published version? i.e.: If I install the package now will I see the print_info_block() in the php?

No I am trying to add a new informational message to the code but its not allowing that..

You can add this line to pfblockerng.inc at line 1765.
https://github.com/pfsense/FreeBSD-ports/blob/devel/net/pfSense-pkg-pfBlockerNG/files/usr/local/pkg/pfblockerng/pfblockerng.inc#L1765

print_info_box("test");

Then hit "save" in IPv4 Tab when editing an Alias to call that function.

So what alternatives/workaround do we have to print a pop-up message?

Well the "usual" way to do it is something like:

if ($_POST['sync']) {
    do_clever_stuff();

    $savemsg = "pfBlockerNG has successfully synced with the server");
}

pkg.php will automatically print an info_box with that messages when the time comes.

I tried that already ... See post #2 above... Add:

pfblockerng.inc Line: 1765
$savemsg = "Test";

Also tried to set $savemsg as a global variable.

It looks like on clicking the save button you are saving the page via jQuery/AJAX and then the function exits without re-drawing the screen, hence you don't see the info_box. THe only thing I see that might be useful is this:

if ($_GET['savemsg'] != "") {
    $savemsg = htmlspecialchars($_GET['savemsg']);
}

This seems to work as expected and might be of use to you:

pkg.php?xml=/pfblockerng/pfblockerng_v4lists.xml&savemsg=This%20is%20a%20test

Added to my browser address bar this produced the print_info_box