<?php
$json = '{"a":1,"b":2}';
echo "<pre>";
var_dump(json_decode($json));
var_dump(json_decode($json, true));
echo "</pre>";
$data = json_decode($json);
foreach($data as $key => $val) { echo $key . " = " . $data->{$key}. "<br/>";  } 
$data = json_decode($json, true);
foreach($data as $key => $val) { echo $key . " = " . $val. "<br/>";  } 
/*
object(stdClass)#1 (2) {
  ["a"]=>
  int(1)
  ["b"]=>
  int(2)
}
array(2) {
  ["a"]=>
  int(1)
  ["b"]=>
  int(2)
}
*/
?>