How to do Redirect in PHP with POST and not GET

https://www.sitepoint.com/community/t/how-to-do-redirect-in-php-with-post-and-not-get/4968

<form name='fr' action='redirect.php' method='POST'>
<input type='hidden' name='var1' value='val1'>
<input type='hidden' name='var2' value='val2'>
</form>
<script type='text/javascript'>
document.fr.submit();
</script>