PHP array with JavaScript objects to JavaScript

Question

If I have an array in JS like this:

{
 "car": "BMW",
 "count": 7 
}

I can generate it from PHP quite easy using this array:

array(
       'car' => 'BMW',
       'count' => 7,
)

and json_encode. This is not a problem.

But what if I have an array in JS like this:

{
   "center": new google.maps.LatLng(-34.397, 150.644),
   "zoom": 8
}

is there also some nice way how to produce it from PHP?

The method above fails because JSON put quotes around "new google.maps.LatLng(-34.397, 150.644)".

Your first example isn't an array, it's an object.

Lee Taylor
– Lee Taylor

2013-07-31 00:07:50 +00:00
Commented Jul 31, 2013 at 0:07 — Lee Taylor
– Lee Taylor, Commented Jul 31, 2013 at 0:07
You are right, sorry for confusion. I'm more PHP than JS ;)

user2042985
– user2042985

2013-07-31 00:21:17 +00:00
Commented Jul 31, 2013 at 0:21 — user2042985
– user2042985, Commented Jul 31, 2013 at 0:21

Jonathan Lonowski · Accepted Answer · 2013-07-31 00:36:24Z

2

JSON doesn't support custom types. It's just meant for passing data and to be available to any consumer, whereas google.maps.LatLng() isn't really "data."

So, you'll have to accomplish this in 2 steps:

You can include the values needed in another PHP array for the JSON:

array(
    'center' => array(
        'lat' => -34.397,
        'lng' => 150.644
    ),
    'zoom' => 8
)

{
    "center": {
        "lat": -34.397,
        "lng": 150.644
    },
    "zoom": 8
}

Then, once parsed to a JavaScript Object, say data:

data.center = new google.maps.LatLng(data.center.lat, data.center.lng);

And, if there are numerous examples of such objects in the data, you can specify a reviver function to try to recognize them and create the instances:

// parse, creating `google.maps.LatLng` from any { lat: ..., lng: ..., ... }
var data = JSON.parse(jsonString, function (key, value) {
    if (typeof value === 'object' && value.lat && value.lng) {
        return new google.maps.LatLng(value.at, value.lng);
    } else {
        return value;
    }
});

Example: http://jsfiddle.net/XXbUU/

Side note: JSON and JavaScript make a stronger distinction between "array" types than PHP does.

"Associative" arrays in PHP become Objects in JSON and JavaScript.
"Non-associative" arrays in PHP become Arrays in JSON and JavaScript.

edited Jul 31, 2013 at 0:36

answered Jul 31, 2013 at 0:06

Jonathan Lonowski

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8 Comments

shennan Over a year ago

To elaborate on Jonathan's answer, you're trying to store functionality within JSON. JSON is used for structuring data, not executing it. new google.maps.LatLng(-34.397, 150.644) is functionality, and needs a processor to evaluate. JSON is processor-independent because it is just a string. Hence your way around would be to store the coordinates and then instantiate them when in the PHP/JS environments.

joequincy Over a year ago

As another sidenote, this is a better practice than passing an arbitrary function call anyway, since that would open up a security vulnerability.

user2042985 Over a year ago

Hmmm, clever :) But not exactly what I want. I want to generate various objects in JS having many properties like new google.maps.LatLng(-34.397, 150.644). Following your way it means that I have to add to JS this second step for any such property. I would like only to add elements to PHP array and not doing this extra step. But I'm afraid that there is no better way than yours :( Anyway thank you for your idea and also for reminding me what is an array/object in JS :)

Jonathan Lonowski Over a year ago

@user2042985 For multiple objects, you can match and replace the Objects with a reviver when parse'ing. See my edit under 2. for an example.

Jonathan Lonowski Over a year ago

@joequincy Though, the JSON can include clues as to the intended type, such as a "$type" property -- "$type": "LatLng" or "$type": "Marker". Then, if (value && value.$type === 'LatLng') ..., etc.

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