optional function arguments

[devinemke]

how do i make function arguments optional? this code produces a "missing argument" error:

function test ($arg)
{
if (isset ($arg)) {echo 'argument given';}
else {echo 'no argument given';}
}

test ();

[PyroX]

function test ($arg="")
{
if (isset ($arg)) {echo 'argument given';}
else {echo 'no argument given';}
}