Online PHP editor | output for aLasP

<?php $array = [ [ "08:30", "09:00", "09:30", "10:00", "14:30", "15:00", "15:30", "16:00", "16:30" ], [ "13:30", "14:00", "14:30", "18:00", "18:30", "19:00" ] ]; function compactTimes( array $times, string $format = 'H:i', string $separation = "30 minutes" ): array { $result = []; $prev = null; foreach ($times as $time) { if (!$prev || $time !== date("H:i", strtotime("+$separation $prev"))) { unset($ref); $ref = [$time, $time]; $result[] =& $ref; } else { $ref[1] = $time; } $prev = $time; } return $result; } var_export( array_map('compactTimes', $array) );