json_encode関数の引数にSImpleXMLElementを渡せる

<?php

$xml_string = '
<Employees>
  <Employee Gender="Male" Age="25">
    <FirstName>Keisuke</FirstName>
    <LastName>Oyama</LastName>
    <ID>123</ID>
  </Employee>
  <Employee Gender="Male" Age="30">
    <FirstName>Ichiro</FirstName>
    <LastName>Suzuki</LastName>
    <ID>456</ID>
  </Employee>
  <Employee Gender="Female" Age="40">
    <FirstName>Hanako</FirstName>
    <LastName>Yamada</LastName>
    <ID>789</ID>
  </Employee>
</Employees>
';
var_dump(json_decode(json_encode(simplexml_load_string($xml_string)), true));
/*
array(1) {
  ["Employee"]=>
  array(3) {
    [0]=>
    array(4) {
      ["@attributes"]=>
      array(2) {
        ["Gender"]=>
        string(4) "Male"
        ["Age"]=>
        string(2) "25"
      }
      ["FirstName"]=>
      string(7) "Keisuke"
      ["LastName"]=>
      string(5) "Oyama"
      ["ID"]=>
      string(3) "123"
    }
    [1]=>
    array(4) {
      ["@attributes"]=>
      array(2) {
        ["Gender"]=>
        string(4) "Male"
        ["Age"]=>
        string(2) "30"
      }
      ["FirstName"]=>
      string(6) "Ichiro"
      ["LastName"]=>
      string(6) "Suzuki"
      ["ID"]=>
      string(3) "456"
    }
    [2]=>
    array(4) {
      ["@attributes"]=>
      array(2) {
        ["Gender"]=>
        string(6) "Female"
        ["Age"]=>
        string(2) "40"
      }
      ["FirstName"]=>
      string(6) "Hanako"
      ["LastName"]=>
      string(6) "Yamada"
      ["ID"]=>
      string(3) "789"
    }
  }
}
*/