<?php

$data = [
	1, 2, 3,
	'',
	4, 5, 6, 7,
	'',
	8, 9, 10, 11, 12, 13,
	''
];
print_r($data);

$newArray = [];
$i = 0;
foreach($data as $item) {
	if(empty($item)) {
		++$i;
		continue;
	}
	else {
		$newArray[$i][] = $item;
	}
}
print_r($newArray);