<?php

// your code goes here

function my_array_merge($array) {
   $result = [];
   foreach($array as $subArray) {
      $result = array_merge($result, $subArray);
   }
   return $result;
} 

$a = [];
$a['one'] = [1,2,3];
$a['two'] = [4,5,6];
print_r(my_array_merge($a));