Decode only the first level of a JSON in PHP - php

Question

The question
I have a JSON string which I would like to decode. However, I only want the first level to be decoded, the rest of the JSON should stay as string values instead of nested arrays.
Using a similar technique, the generated array (with nested string values) should be parsed back to a JSON string. When using these decode and encode in succession the result should be the original JSON string.
Short and simple, right?
I would also rather not interpret the nested values of the JSON, as those may or may not be valid JSON. If there is no way around this, then so be it.
Example
Please note that all these slashes are just to keep it a valid PHP string, they are not part of the input. There are no escaped quotes in the input.
When a JSON string like this is put in:
"{
\"foo\": \"bar\",
\"nested\": {
\"nested_key\": \"nested_value\"
},
\"another_top_level_key\": \"some_useful_value\"
}"
This should be the output:
[
"foo" => "bar",
"nested" => "{ \"nested_key\": \"nested_value\" }",
"another_top_level_key" => "some_useful_value"
]
When using var_dump, it should look like this:
array(3) {
["foo"]=>
string(3) "bar"
["nested"]=>
string(32) "{ "nested_key": "nested_value" }"
["another_top_level_key"]=>
string(17) "some_useful_value"
}
Pay attention to the fact that when using var_dump, the quotes are not escaped and thus no slashes exist in the string (the nested quotes are not escaped).
When that array is run through the second function (the encoder), the original JSON string should be returned.
Things I've tried:
I tried setting the $depth of json_decode() to 1. This, however, only throws exceptions when the limit has been reached.
I tried decoding the whole string using json_decode() and then looping over the top-level key-value pairs to run json_encode() over any value that is an array (which should indicate a nested value). The end result was fine at first, but when converting back to a JSON string it escaped the double quotes with slashes. In that case, the end result isn't the same as the original, as the end result includes slashes.
Notes
Even though this question has a very similar title to this one, that one doesn't actually contain answers for its title. There is only an answer on how to transform the invalid JSON string to a valid JSON.
I'd rather not use any RegEx, as that just makes my life more complex than it needs to be ;). But if it can't be avoided, then that's life I guess.
As requested by deceze:
$jsonString = "{ \"foo\": \"bar\", \"nested\": { \"nested_key\": \"nested_value\" }, \"another_top_level_key\": \"some_useful_value\" }";
$decoded = json_decode($jsonString, true);
foreach ($decoded as $key => $value) {
if (is_array($value)) {
$decoded[$key] = json_encode($value);
}
}
$encoded = json_encode($decoded);
var_dump($encoded);
The result is this:
string(102) "{"foo":"bar","nested":"{\"nested_key\":\"nested_value\"}","another_top_level_key":"some_useful_value"}"
Which means that in the end, it did escape the quotes, which is something I cannot accept :(.

Answer 1

Use a function to check when you have an element as array then convert back to json:
<?php
$json = "{
\"foo\": \"bar\",
\"nested\": {
\"nested_key\": \"nested_value\"
},
\"multinested\": {
\"multinested_key\": {
\"multinested_key\": \"nested_value\"
}
},
\"another_top_level_key\": \"some_useful_value\"
}";
$array = json_decode($json, true);
foreach($array as &$item) {
if (is_array($item)) {
$item = json_encode($item);
}
}
print_r($array);
Output:
Array
(
[foo] => bar
[nested] => {"nested_key":"nested_value"}
[multinested] => {"multinested_key":{"multinested_key":"nested_value"}}
[another_top_level_key] => some_useful_value
)

Answer 2

The trick is to use the decode twice:
$array = json_decode(json_decode($json, true), true);
print_r($array);