<pre>
<?php
if (isset($_POST)){
    var_dump($_POST);
}
/*
array(1) {
  ["api"]=>
  array(1) {
    ["etsy"]=>
    array(1) {
      ["name"]=>
      string(4) "name"
    }
  }
}
*/
?>
</pre>
<form method="post" action="" >
<input type="text" name="api[etsy][name]" value="name"/>
<input type="submit" value="go"/>
</form>