<?php
$dados_POST = array('meu_campo' => '<span style="display: none"> </span>');
$str = $dados_POST['meu_campo'];
echo $str;
PD9waHAKCiRkYWRvc19QT1NUID0gYXJyYXkoJ21ldV9jYW1wbycgPT4gJzxzcGFuIHN0eWxlPSJkaXNwbGF5OiBub25lIj4mbmJzcDs8L3NwYW4+Jyk7Cgokc3RyID0gJGRhZG9zX1BPU1RbJ21ldV9jYW1wbyddOwplY2hvICRzdHI7Cg==