3v4l.org

run code in 300+ PHP versions simultaneously
<?php $master = array(); $arrColors = array('R', 'B', 'G' ,'Y'); $arrNumbers = array('1', '2', '3', '4'); foreach($arrColors as $color) { foreach($arrNumbers as $num) { $arr2 = array_push($master, $num); //$master += array($color => $num); //echo $color.' => '.$num; //echo "\n"; } array_push($arr2, $color); } print_r($master);

preferences:
47.6 ms | 402 KiB | 5 Q