Is basically "strip_tags", but supports a couple of flags:
<?php
$flags = array(
'FILTER_FLAG_NO_ENCODE_QUOTES', 'FILTER_FLAG_ENCODE_LOW',
'FILTER_FLAG_ENCODE_HIGH', 'FILTER_FLAG_STRIP_LOW',
'FILTER_FLAG_STRIP_HIGH'
);
$filter = FILTER_SANITIZE_STRING;
include 'presentations/slides/input-filter/render-form.php';
include 'presentations/slides/input-filter/check-data.php';
?>
Output