<?php
$members = [
    'myname' => ['userid' => 52, 'age' => 46],
    'isname' => ['userid' => 22, 'age' => 47],
    'yourname' => ['userid' => 47, 'age' => 85]
];
$result=array_keys($members);
$result=array_combine($result,$result);
$result=array_merge_recursive($members,$result);
print_r($result);