- array_reduce: documentation ( source)
- var_export: documentation ( source)
- array_fill_keys: documentation ( source)
- array_keys: documentation ( source)
<?php
$mode[1] = [1, 2, 5, 6];
$mode[0] = [3, 4, 7, 8];
var_export(
array_reduce(
array_keys($mode),
fn($result, $k) => $result += array_fill_keys($mode[$k], $k),
[]
)
);