The reason this happens can be demonstrated quite easily...
class foo{
public $bar = 'bar';
}
$json = json_encode(new foo);
echo $json."\n\n";
print_r(json_decode($json));
Output
{"bar":"bar"}
stdClass Object
(
[bar] => bar
)
Sandbox
As you can see the output {"bar":"bar"}
contains no information about what if any class this was, it could have been ['bar'=>'bar']
and the JSON would be the same... Then when decoding it, you don't have json_decode
set to return as an array (second argument set to true), which is fine as that's not really what you want, but when it's set that way you get stdClass objects instead of an associative array for items with non-numeric keys. In short there is no way to recover the class "foo" from the json {"bar":"bar"}
as that information does't exist (you can make it exist, but that's another tale for another day).
Using serialize we get something very different.
class foo{
public $bar = 'bar';
}
$json = serialize(new foo);
echo $json."\n\n";
print_r(unserialize($json));
Output
O:3:"foo":1:{s:3:"bar";s:3:"bar";}
foo Object
(
[bar] => bar
)
Sandbox
This O:3:foo
means an Object with a class name 3 in length named "foo". So it preserves that information for PHP to use when "decoding" the data.
The whole thing reads like this:
Object (3) "foo" with 1 property named (s)tring (3) "bar" with a value of (s)tring (3) "bar", or something like that.
Make sense.
AS a note PHP's serialize is less portable then JSON, as it only works in PHP, It's also much harder to manually edit then JSON, but if you really want to encode a class than that is the easiest way to do it. That said you can also "repopulate" the class from JSON data, but that can also be hard to maintain.