Вася

$arr_finished = $arr1 + $arr2 + $arr3 + ...
$arr_finished = array_walk($arr_finished, function(&$v, $k) {
    $v = isset($arr1[$k]) ? $arr1[$k] : "";
});

select t2.*, t1.content
from tb2 t2 left join tb1 t1 on t2.id = t1.id

Select o.* from (
Select max(updated_at) as maxdate,  sender_user_id, recipient_user_id
from chattable 
group by sender_user_id, recipient_user_id
) as t
join chattable as o on t.sender_user_id=o.sender_user_id and t.recipient_user_id=o.recipient_user_id and t.maxdate=o.upadet_at

<input type="button" id="magicbtn" />
<div id="magichtml"></div>
<script>
$(document).on("click", "#magicbtn", function() {

$.ajax({
  url: "/ajax/magic.php"
}).done(function(result) {
  $( "#magichtml").html(result);
});
});

CModule::IncludeModule("iblock");

	$res = CIBlockElement::GetList(
		Array("NAME" => "ASC"), 
		Array("IBLOCK_ID"	 => 8, "ID" => 5346), 
		false, 
		false, 
		Array(
			'ID',
			'NAME',
			'PROPERTY_MANUFACTURER.PROPERTY_TESTLINK',
		)
	);
	while ($item = $res->GetNext())
	{
		echo '<pre>';
		print_r($item);
		echo '</pre>';
	}

var t = JSON.parse('"\u003Cdiv\u003Etest\u0442\u0435\u0441\u0442\u003C\/div\u003E"')
console.log(t);  // =>  "<div>testтест</div>"