Using Ternary Operator without the Else statement PHP

Can you use the Ternary Operator in PHP without the closing 'else' statement? I've tried it and it's returning errors. Google search isn't yielding anything, so I think the answer is probably no. I just wanted to double check here. For instance:

if ( isset($testing) {
  $new_variable = $testing;
}

Will only set $new_variable if $testing exists. Now I can do

$new_variable = (isset($testing) ? $testing : "");

but that returns an empty variable for $new_variable if $testing isn't set. I don't want an empty variable if it's not set, I want the $new_variable to not be created.

I tried

$new_variable = (isset($testing) ? $testing);

and it returned errors. I also tried

$new_variable = (isset($testing) ? $testing : );

and it also returned errors. Is there a way to use the Ternary Operator without the attached else statement, or am I stuck writing it out longhand?