Does ternary operator can only do one kind of condition?

Question

ternary make code concise and readable, I'm curious about how to change the following if condition to ternary operator:

var1 = if(true){'a'};

I try the following

var1 = true? 'a': ;

since it require nothing to do with false condition, I leave blank after :, but apparently it gives me a error.

Is there a way to do this?

--------update---------

The intention of using the above example is that I want to simplify the problem, however it made everyone more confuse, so I post my original code:

if($_SERVER['REQUEST_METHOD'] == 'GET'){ $sub_count = 0; }

$sub_count = $_SERVER['REQUEST_METHOD'] == 'GET'? 0 : ;

how to change the if condition to ternary ?

Answer 1

$sub_count = null;
$sub_count = $_SERVER['REQUEST_METHOD'] == 'GET'? 0 : null;

// To check:
if(!isset($sub_count))
{
   // Do something because $_SERVER['REQUEST_METHOD'] != 'GET'
} else {
    if($sub_count===0)
    {
        // REQUEST METHOD IS GET
    }
}