为什么printer_list功能不起作用

I tried the below sample code to get the list of shared printers name but i did not get the expected result. Anybody explain me why it is happening?

<?php
   var_dump(printer_list(PRINTER_ENUM_LOCAL | PRINTER_ENUM_SHARED));
?>

Try this code

<?php
$printers = printer_list ( PRINTER_ENUM_LOCAL );
print_r($printers);
?>