for($x=1; $x<count($output['ADL']); $x++) {
		$i+=1;
		$key = current($output['ADL']);
		$range[$i]['lo'] = $key;
		while(in_array(($key), $output['ADL'])) {
				$range[$i]['hi'] = $key;
				$key += 1; $x++;
				next($output['ADL']);
			}
	}

print_r($range);

/* output 
Array
(
    [1] => Array
        (
            [lo] => 5000
            [hi] => 5115
        )

    [2] => Array
        (
            [lo] => 5125
            [hi] => 5127
        )

    [3] => Array
        (
            [lo] => 5158
            [hi] => 5169
        )

    [4] => Array
        (
            [lo] => 5810
            [hi] => 5999
        )

)
*/