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Generating a unique key structure from JSON


cindreta
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Go to solution Solved by requinix,

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Hi guys,

i've been struggling with a problem regarding reading the JSON structure, decoding it and than trying to extract a UNIQUE key structure from it.

 

So let me show you by example what im trying to do here. Let's take a look at this JSON:

{
   "status": true,
   "message": "Everything was ok",
   "posts":[
      {
         "id": 1,
         "post_type": "type_a",
         "posted_on": "",
         "updated_on":"",
         "user":{
            "id": 1,
            "name": ""
         },
         "num_comments": 2,
         "comments":[
            {
               "id": 1,
               "comment":"",
               "commented_on":"",
               "user":{
                  "id": 1,
                  "name": "",
                  "profile_image": ""
               }
            },
            {
               "id": "",
               "comment": "",
               "commented_on": "",
               "user":{
                  "id": "",
                  "name": "",
                  "profile_image":""
               }
            }
         ],
         "message": "",
         "images":[
            {
               "image":"",
               "image_large":""
            }
         ]
      },
      {
         "id": 2,
         "post_type": "type_b",
         "posted_on": "",
         "updated_on":"",
         "notes":{
            "id": 1,
            "name": ""
          },
         "user":{
            "id": 1,
            "name": ""
         },
         "num_comments":"0",
         "images":[
            {
               "image":"",
               "image_large":""
            }
         ]
      },
   ]
}

So as you can see from the example the structure of the two post arrays varies, one has a comments section, the other one doesnt, one has a notes section, the other one doesnt etc etc. What i would somehow like to be able to do is extract a UNIQUE JSON structure for this document. Meaning i only care about the KEYS not the values and i wanna show the user what can he expect and what are the possibilities.

 

Here is my code so far:

function keys_are_equal($array1, $array2, $key) {
      return !array_diff_key($array1, $array2) && !array_diff_key($array2, $array1);
    }

    function prettyParseJson($json) {
        $decoded = json_decode($json, true);
        if($decoded && is_array($decoded)) {
            return recursiveJsonRead($decoded);
        }
    }

    function recursiveJsonRead($data) {
        
        $previous_array = array();
        $unique_array = array();

        foreach ($data as $key => $val) {
              
            if(is_array($val)) {
                if(!empty($val)) {
                  
                    if(keys_are_equal($previous_array, $val, $key)) {
                     
                    } else {

                        $unique_array[$key] = gettype($val);
                        $unique_array[$key] = recursiveJsonRead($val);
                        $previous_array = $val;
                    }
                }

            } else {
                $unique_array[$key] = gettype($val);
            }
        }
        return $unique_array;
    }

As you can see im trying to decode the json, im trying to walk through it and extract all keys and their types but currently it only works if the structure is ALWAYS the same, if it varies if creates duplicates of keys that are already defined in a previous array. And again i hope im explaing this correctly but all i wanna do is be able to load a JSON file and read out its UNIQUE key structure.

 

If someone can help me out it would be great cos im losing my mind over it.

 

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The keys aren't too helpful without knowing what the data is behind them. Like, what is "post_type"? Is "posted_on" a timestamp or a date string? Which of these can have empty values and which cannot? For types, what about the occasional "id" that is an empty string or an integer?

 

What output are you trying to get? I'm figuring

{
	"status": "bool",
	"message": "string",
	"posts": [
		{
			"id": "int",
			"post_type": "string",
			"posted_on": "string",
			"updated_on": "string",
			"user": {
				"id": "int",
				"name": "string"
			},
			"num_comments": "int",
			"comments": [
				{
					"id": "int",
					"comment": "string",
					"commented_on": "string",
					"user": {
						"id": "int",
						"name": "string",
						"profile_image": "string"
					}
				}
			],
			"message": "string",
			"images": [
				{
					"image": "string",
					"image_large": "string"
				}
			],
			"notes": {
				"id": "int",
				"name": "string"
			}
		}
	]
}
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I'll come back with code later (got stuff to do) but some talking points:

 

- Decoding using objects and not associative arrays - arrays and objects have different meanings in JSON and you'll need to know which is which

- Traverse the source and storage arrays at the same time, recursively

- If the source value is scalar then use its type in storage if there isn't already one

- If the source value is an array then set/reuse a [0] in storage and traverse each item [n] in the source subarray with storage's [0], as in

foreach ($source as $item) {
	recurse($item, $storage[0]); // each $source[$n] but always $storage[0]
- If the source value is an object then recurse as expected
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  • Solution
function parse_structure($source, $output = null) {
if (is_object($source)) {
// objects are easy: recurse over all the properties
$output || $output = [];
foreach (get_object_vars($source) as $key => $value) {
$output[$key] = parse_structure($value, isset($output[$key]) ? $output[$key] : null);
}
return $output;
} else if (is_array($source)) {
// arrays should contain all of the same data type
$output || $output = [];
if (is_scalar($source[0])) {
// foreach on the array would be wasteful - just check the first item
isset($output[0]) || $output[0] = gettype($source[0]);
} else {
// recurse over all the items and put the merged structure into [0]
isset($output[0]) || $output[0] = [];
foreach ($source as $arrayitem) {
$output[0] = parse_structure($arrayitem, $output[0]);
}
}
return $output;
} else {
// if $output already has a type then keep it
return $output ?: gettype($source);
}
}
$output = parse_structure(json_decode($json) /* decode with objects */);
  • Like 1
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Just tested and works GREAT! Thank you so much. I tested on two JSONs and one one of them i get a NOTISE on this:

 

f (is_scalar($source[0])) {

saying:

 

Notice: Undefined offset: 0

 

But on other example it worked great. Wow this will help me so much. You are a true magician : D

 

PS. while i was extensively Googling i found this tool: https://jsonschema.net/#/editor it goes a step further and generates a JSON schema based on the JSON input which is also good but from what i see it uses some kind of an API from Google which i can't seem to find.

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