- var_dump: documentation ( source)
- json_decode: documentation ( source)
<?php
$son = '{
"1":{ "id":"1", "name":"jack" },
"2":{ "id":"2", "name":"john" }
}';
$json = json_decode($son);
//var_dump($json);
var_dump($json->{'1'}); // correct result
$index = 1;
var_dump($json->$index); // correct result