exec results in cannot open tty-output

[curlyroger]

I'm trying to develop a CLI PHP application that uses the Linux command "dialog" for menu control purposes. Here is example code I am trying to run:

#!/usr/bin/php -q
<?

$cmd='dialog --backtitle "Test" --title "Main Menu" --menu "" 10 30 3 "Option 1" "" "Option 2" "" "Option 3" ""';

`$cmd`;

?>

Regardless of using backtickets, passthru, exec, or system, running this code via command line always produces the "cannot open tty-output" error.

How can I overcome this? I'd like to use dialog to build and run my menus and control everything else via PHP.

TIA.