3v4l.org

run code in 300+ PHP versions simultaneously
<?php $f=fn($a,$f)=>$a?[...array_shift($a),...$f(array_reverse($a?next($a)?array_map(null,...$a):array_chunk($a[0],1):$a),$f)]:$a; print_r( $f([[1, 2, 3, 4], [12, 13, 14, 5], [11, 16, 15, 6], [10, 9, 8, 7]], $f) );
based on R0mqJ
Output for 7.4.0 - 7.4.13, 8.0.0 - 8.0.2
Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 [6] => 7 [7] => 8 [8] => 9 [9] => 10 [10] => 11 [11] => 12 [12] => 13 [13] => 14 [14] => 15 [15] => 16 )
Output for 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.26
Parse error: syntax error, unexpected '=>' (T_DOUBLE_ARROW) in /in/JDGfH on line 3
Process exited with code 255.
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29
Parse error: syntax error, unexpected T_DOUBLE_ARROW in /in/JDGfH on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1, 5.0.0 - 5.0.5
Parse error: parse error, unexpected T_DOUBLE_ARROW in /in/JDGfH on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error in /in/JDGfH on line 3
Process exited with code 255.