Online PHP editor | refs for bKB54

<?php $array = [ 'company 1' => [1981 => 1, 1945 => 3], 'company 2' => [1990 => 18, 2005 => 13], 'company 3' => [1950 => 6, 2012 => 9] ]; if ($array) { $firstKeys = array_keys(array_shift($array)); $minYear = min($firstKeys); $maxYear = max($firstKeys); } else { $minYear = null; $maxYear = null; } foreach ($array as $row) { foreach ($row as $year => $value) { if ($year > $maxYear) { $maxYear = $year; } elseif ($year < $minYear) { $minYear = $year; } } } echo "MinYear = $minYear, MaxYear = $maxYear";