Create JSON using PHP with data which contains JSON - php

Question

How can I create JSON using PHP with data which contains JSON without including a bunch of escape characters in the JSON, and without converting JSON first to an array or object, and then back to JSON?
<?php
/*
GIVEN: Data from DB contained in array $a.
I know that sometimes JSON shouldn't be stored in a DB, but please assume this is a good case for doing so.
*/
$a[0]=json_encode(['a'=>5,'b'=>'hello']);
$a[1]=json_encode(['a'=>2,'b'=>'how are you']);
$a[2]=json_encode(['a'=>7,'b'=>'goodby']);
$o=[
['x'=>321,'y'=>$a[0]],
['x'=>123,'y'=>$a[1]],
['x'=>111,'y'=>$a[2]],
];
echo('<pre>'.print_r($o,1).'</pre>');
echo(json_encode($o));
/*
Undesired result containing a bunch of escape characters. Granted, they are benign, however, will increase network trafic.
[{"x":321,"y":"{\"a\":5,\"b\":\"hello\"}"},{"x":123,"y":"{\"a\":2,\"b\":\"how are you\"}"},{"x":111,"y":"{\"a\":7,\"b\":\"goodby\"}"}]
*/
$o=[
['x'=>321,'y'=>json_decode($a[0])],
['x'=>123,'y'=>json_decode($a[1])],
['x'=>111,'y'=>json_decode($a[2])],
];
echo('<pre>'.print_r($o,1).'</pre>');
echo(json_encode($o));
/*
Desired result, however, is there a more efficient way to do this?
[{"x":321,"y":{"a":5,"b":"hello"}},{"x":123,"y":{"a":2,"b":"how are you"}},{"x":111,"y":{"a":7,"b":"goodby"}}]
*/

Answer 1

No, there is no faster way then to decode, mutate and encode again.
You could however combine the decoding code closely with your database queries. If you have a data model class, you would do the decoding there, so that the code that calls this service will never see the JSON, but always the decoded data.
Then, again, in the data model, where you write to the database, you would perform the JSON encoding at the last moment.
This way you hide the JSON factor behind the walls of the data layer, and the rest of the application will not have to be aware of that.
Manipulating JSON directly
Another solution consists of writing a library that can juggle with JSON, giving possibilities to set values inside JSON without the caller having to decode/encode. This option requires much more code (or you could find an existing library), and so it is not really my first recommendation. But here is a naive example of a function that could exist in that library:
function json_set($json, $path, $value) {
$arr = json_decode($json, true);
$ref =& $arr;
$props = explode("/", $path);
$finalProp = array_pop($props);
foreach ($props as $key) {
if (!isset($ref[$key])) $ref[$key] = [];
$ref =& $ref[$key];
}
$obj = json_decode($value);
$ref[$finalProp] = $obj ? $obj : $value;
return json_encode($arr);
}
This allows you to provide an existing JSON string, a path pointing to a certain spot inside that JSON, and a value that should be put there. That value could itself also be JSON.
Here is how you would use it in your case, given the JSON values in $a which you got from the database:
$o=json_encode([
['x'=>321],
['x'=>123],
['x'=>111],
]);
$o = json_set($o, '0/y', $a[0]);
$o = json_set($o, '1/y', $a[1]);
$o = json_set($o, '2/y', $a[2]);
echo $o;
Output:
[{"x":321,"y":{"a":5,"b":"hello"}},
{"x":123,"y":{"a":2,"b":"how are you"}},
{"x":111,"y":{"a":7,"b":"goodby"}}]