Question

Is it possible to use a PHP constant within a PHP function?

// in a different file
DEFINE ('HOST', 'hostname');
DEFINE ('USER', 'username');
DEFINE ('PASSWORD', 'password');
DEFINE ('NAME', 'dbname');

// connecting to database
function database()
{
    // using 'global' to define what variables to allow
    global $connection, HOST, USER, PASSWORD, NAME;
    $connection = new mysqli(HOST, USER, PASSWORD, NAME)
        or die ('Sorry, Cannot Connect');
    return $connection;
}

Answer 1

You don’t need to declare them in global in the function, PHP recognises them as globals.

function database()
{
  // using 'global' to define what variables to allow
  global $dbc;
  $connection = new mysqli(HOST, USER, PASSWORD, NAME)
      or die ('Sorry, Cannot Connect');
  return $connection;
}

From php.net:

Like superglobals, the scope of a constant is global. You can access constants anywhere in your script without regard to scope. For more information on scope, read the manual section on variable scope.