<?php

$_POST['♠♣♥♦'] = 'value1';
$_POST['\'\'\'\''] = 'value2';
$_POST['<?php echo "Hello World"; ?>'] = 'value3';
$_POST['     '] = 'value4';
$_POST[''] = 'value5';
$_POST['@#$%^&*()'] = 'value6';

print_r($_POST);

Array
(
    [♠♣♥♦] => value1
    [''''] => value2
    [<?php echo "Hello World"; ?>] => value3
    [     ] => value4
    [] => value5
    [@#$%^&*()] => value6
)