JSFiddle - React, Tailwind, and code Playground

HTML

<form method="post">
    <select name='PreviousReceiver' onchange='if(this.value != 0) { this.form.submit(); }'>
         <option value='0'>Contact List</option>
         <option value='1' name="op">blah</option>
         <option value='2'>blah2</option>
         <option value='3'>blah3</option>
    </select>
</form>
<?php
$var = $_POST['op'];
echo $var;

?>