This question has been answered by Bruno17. See the first response.
&where=`[{"dateEnd:>":"2017-02-28","OR:dateEnd:=":null},{"AND:dateFrom:>":"2017-02-21"}]`
<?php
//&value=`[[filterbetween? &items=`[[*yourMIGXtv]]` &start=`2017-02-21` &end=`2017-02-28`]]`
$items = json_decode($items,true);
$filtered = array();
if (is_array($items)){
foreach ($items as $item){
if ($item['dateFrom'] > $start && ($item['dateEnd'] < $end || empty($item['dateEnd']))){
$filtered[] = $item;
}
}
}
return json_encode($filtered);
&value=`[[filterbetween? &items=`[[*yourMIGXtv]]` &start=`2017-02-21` &end=`2017-02-28`]]`