- print_r: documentation ( source)
<?php
$input = [1, 1, 1, 2, 2, 2, 1, 1, 2, 2, 1];
$output = [];
$idx = -1;
$prev = null;
foreach($input as $val) {
if($prev !== $val) {
++$idx;
}
$output[$idx][] = $val;
$prev = $val;
}
print_r($output);