3v4l.org

run code in 500+ PHP versions simultaneously
<?php $array = [1, 2, 3, 4, 5, 6, 7, 8, 9]; $result = []; while ($array) { $result[] = implode(', ', array_splice($array, 0, 4)); } var_export($result);
Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.31, 8.4.1 - 8.4.22, 8.5.0 - 8.5.7
array ( 0 => '1, 2, 3, 4', 1 => '5, 6, 7, 8', 2 => '9', )

preferences:
95.59 ms | 1269 KiB | 4 Q