PHP JSON decode: array with '$' problem

Question

I have the following JSON file as input,

{
  "$type": "NanoWebInterpreter.WebInputData, NanoWebInterpreter",
  "NBBList": {
    "$type": "System.Collections.Generic.List`1[[monoTNP.Common.NBB, monoTNP.Common]], mscorlib",
    "$values": [
      {
        "$type": "monoTNP.Common.NBB, monoTNP.Common",
        "ID": "id-0065-00000003",
        "MPList": {
          "$type": "System.Collections.Generic.List`1[[monoTNP.Common.MP, monoTNP.Common]], mscorlib",
          "$values": [
            {
              "$type": "monoTNP.Common.EllipticalMP, monoTNP.Common",
              "Eccentricity": 1.0,
              "ID": "id-0065-00000006",
              "ParticleIndex": -1,
              "DispersionInteractionStrength": 0.0,
              "DispersionInteractionRange": 2.5,
              "CharacteristicSize": 0.0,
              "CenterOfMass": "<0,0,0>",
              "OrientationVector": "<>"
            },
            {
              "$type": "monoTNP.Common.CubeMP, monoTNP.Common",
              "ID": "id-0065-00000005",
              "ParticleIndex": -1,
              "DispersionInteractionStrength": 0.0,
              "DispersionInteractionRange": 2.5,
              "CharacteristicSize": 0.0,
              "CenterOfMass": "<0,0,0>",
              "OrientationVector": "<>"
            },
            {
              "$type": "monoTNP.Common.CircularMP, monoTNP.Common",
              "ID": "id-0065-00000004",
              "ParticleIndex": -1,
              "DispersionInteractionStrength": 0.0,
              "DispersionInteractionRange": 2.5,
              "CharacteristicSize": 0.0,
              "CenterOfMass": "<0,0,0>",
              "OrientationVector": "<>"
            }
          ]
        },

etc.

My ultimate goal is to trace this tree recursively, wrapping each key/object name with <ul> tags, and the properties at the "ParticleIndex" level in some kind of <form> structure, but I can't figure out how to index into the two '$values' arrays.

This is the code that I have been manipulating to learn how each element(object or array) is accessed:

foreach ($json->NBBList->'$values'[0] as $key => $value){
    var_dump($key);
    echo "\n".var_dump($value);
    echo "\n\n\n";
}

This obviously doesn't work because the index of values is outside of the string, but when it is on the inside, PHP interprets it as part of the string.

Is there a way for me to index into each element of the '$values' array, and ultimately in a for loop?

I'm thinking using the "true" property of JSON decode might be a better solution...

Possible duplicate of: stackoverflow.com/questions/6264598/php-decoding-json — hakre
– hakre, Commented Jun 10, 2011 at 18:41

NikiC · Accepted Answer · 2011-06-10 18:31:06Z

6

You can access object properties with names that contain special characters using this notation:

$json->NBBList->{'$values'}[0]

I don't think that this behavior is documented anywhere, but you can find it in the PHP grammar (see definition of variable_name, which is used in object_dim_list, which is used in object_property).

answered Jun 10, 2011 at 18:31

NikiC

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3 Comments

salathe Over a year ago

For what it is worth, there is an example of this in the json_decode() docs.

NikiC Over a year ago

@salathe: Ah okay. I have looked for the docs in the OOP section. Who could have thought that they've put it into the JSON documentation ^^

salathe Over a year ago

This question gets asked a lot so an example (like with SimpleXML) makes sense. :)

phihag · Accepted Answer · 2011-06-10 18:29:15Z

4

Set the assoc parameter of json_decode to false to get arrays(dictionaries) instead of objects:

$json = json_decode($jsonInput, true);
foreach ($json['NBBList']['$values'][0] as $key => $value){
    var_dump($key);
    echo "\n";
    var_dump($value);
    echo "\n\n\n";
}

answered Jun 10, 2011 at 18:29

phihag

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Comments

gen_Eric · Accepted Answer · 2011-06-10 18:30:33Z

1

foreach($json->NBBList->{'$values'}[0] as $key=>$value){

You can use curly braces around the string to access properties of an object with special characters.

answered Jun 10, 2011 at 18:30

gen_Eric

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Comments

Ryan · Accepted Answer · 2011-06-10 18:30:13Z

-2

Have you tried something like?

$show_values = $values[0];

foreach ($json->NBBList->'$show_values' as $key => $value){
var_dump($key);
echo "\n".var_dump($value);
echo "\n\n\n";

Just an idea, I'm not sure how well it will work

answered Jun 10, 2011 at 18:30

Ryan

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2 Comments

Matthew Over a year ago

You must wrap the odd name with {''} even if you want to iterate over it.

Ryan Over a year ago

Thanks for the pointer, seeing the json_decode string in another post reminded me just now

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