3v4l.org

run code in 500+ PHP versions simultaneously
<?php $arr = [2,5,1,12,-5,4,-1,3,-3,20,8,7,-2,6,9]; $a = $arr; asort($a); $a = array_chunk($a, 5); $output = []; $idx = 0; while($a){ if($idx++ % 2){ $b = array_pop($a); arsort($b); }else{ $b = array_shift($a); } $output = array_merge($output, $b); } var_dump($output);

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112.44 ms | 1457 KiB | 5 Q