- var_dump: documentation ( source)
- json_decode: documentation ( source)
- array_keys: documentation ( source)
<?php
var_dump(json_decode('{"4":"Taaaaa"}'));
$array = (array)(json_decode('{"4":"Taaaaa"}'));
var_dump(array_keys($array));
$key = "4";
var_dump($key, $array, $array[(string)$key]);