- var_export: documentation ( source)
- asort: documentation ( source)
- array_walk: documentation ( source)
<?php
$mainArr = [
[125 => 'B', 127 => 'A', 178 => 'Z', 78 => 'G'],
[111 => 'X', 127 => 'K', 108 => 'J', 708 => 'P'],
[125 => 'L', 127 => 'M', 178 => 'Q', 78 => 'A'],
];
array_walk($mainArr, fn(&$subarray) => asort($subarray));
var_export($mainArr);