Online PHP editor | output for v24DG

<?php $openTimeslots = [ '02-09-2021' => [ '8:00-10:00', '16:00-19:00' ], '03-09-2021' => [ '7:00-10:00', '16:15-19:00', '14:00-16:00', '13:00-14:15' ], '04-09-2021' => [ '7:15-10:00', '15:15-18:15' ], '05-09-2021' => [ '8:15-8:45', '9:15-9:45', '16:15-19:00', ] ]; function slotToInts($slot) { return sscanf(str_replace(':', '', $slot), "%d-%d"); } $commons = array_map('slotToInts', array_shift($openTimeslots)); foreach ($openTimeslots as $slots) { $newCommons = []; foreach ($slots as $slot) { [$start, $end] = slotToInts($slot); foreach ($commons as [$commonStart, $commonEnd]) { $newCommonStart = null; $newCommonEnd = null; if ($start >= $commonStart && $start < $commonEnd) { $newCommonStart = $start; } if ($end > $commonStart && $end <= $commonEnd) { $newCommonEnd = $end; } if ($newCommonStart || $newCommonEnd) { $newCommons[] = [ $newCommonStart ?? $commonStart, $newCommonEnd ?? $commonEnd ]; } } } $commons = $newCommons; } var_export( array_map( fn($subarray) => implode('-', preg_replace('~(?=\d{2}(?:-|$))~', ':', $subarray)), $commons ) );