Saving an object as JSON, and then loading it later?

Question

I know how to JSON encode and decode an object. That's no biggie. However, I've reached a situation where I need to save $this as a JSON string, and then later, populate $this's attributes from that JSON string.

In other words, I don't want to get a new instance of an object with the data from the JSON string, I want to apply it to an existing object.

How can I do that?

If an attribute is currently defined on $this but not defined on your encoded object, what do you want to happen with that attribute when you apply the encoded data to $this? — FoolishSeth
– FoolishSeth, Commented Apr 24, 2013 at 14:50
Nothing. Leave the attribute of $this to its old value. My object always has its attributes fully populated. — Mathias Lykkegaard Lorenzen
– Mathias Lykkegaard Lorenzen, Commented Apr 24, 2013 at 14:51
You can just use encode inside your class so you have the json inside your object as an object. Like $instance->jsonecodestuf->etc — botenvouwer
– botenvouwer, Commented Apr 24, 2013 at 14:53

FoolishSeth · Accepted Answer · 2013-04-24 15:01:12Z

1

You can get the defined attributes of an object using get_object_vars() http://php.net/manual/en/function.get-object-vars.php

class MyClass
{
    function populateFromJSON($data)
    {
        $o = json_decode($data);
        $attributes = get_object_vars($o);
        if (is_array($attributes)) {
            foreach ($attributes as $name => $val) {
                $this->$name = $val;
            }
        }
    }
}

edited Apr 24, 2013 at 15:01

answered Apr 24, 2013 at 14:55

FoolishSeth

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3 Comments

Phill Sparks Over a year ago

Why not just use json_decode($data, true) which returns arrays instead of objects.

FoolishSeth Over a year ago

That leads to another issue with this answer. How does it handle attributes which are themselves objects? Not very well.

Phill Sparks Over a year ago

Very true; especially if they're instances of other objects, rather than just stdClass. There's no quick and dirty solution that solves all.

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