<?php

$feat = ['featured', 'featured', 'featured'];
$no_feat = ['brrh', 'brrh', 'brrh', 'brrh','brrh', 'brrh', 'brrh', 'brrh', 'brrh', 'brrh', 'brrh', 'brrh'];
$all = [];
$h = 0;
$all_len = count($feat) + count($no_feat);
for($i = 0; $i < $all_len; $i++) {
	if($i%5 == 0 && count($feat) > 0) {
		$all[] = array_shift($feat);
		$h++;
		continue;
	}
	if(count($no_feat) > 0) {
		$all['no_feat' .$h][] = array_shift($no_feat);
	}
	else {
		$all[] = array_shift($feat);
	}
}
print_r($all);