elseif Using Ternary Operators in php [duplicate]

This question already has an answer here:

• PHP ternary operator not working as expected 4 answers

I am trying to use elseif in php to compare string and push position in array but I can't figure out what I am doing wrong. Here's what I have done.

<?php
$inp         = "Monday";
$pos_su      = 0;
$pos_mo      = 0;
$pos_tue     = 0;
$pos_wed     = 0;
$pos_thu     = 0;
$pos_fri     = 0;
$schedules[] = [
    'Day'      => $inp,
    'Position' => ($inp === 'Sunday') ? $pos_su++ :
    ($inp === 'Monday') ? $pos_mo++ :
    ($inp === 'Tuesday') ? $pos_tu++ :
    ($inp === 'Wednesday') ? $pos_wed++ :
    ($inp === 'Thursday') ? $pos_thu++ :
    ($inp === 'Friday') ? $pos_fri++ : 0,

];
var_dump($schedules);
var_dump($pos_mo);