Append data to JSON array using PHP

Question

I need to append a new object to a JSON array using PHP.

The JSON:

{
   "maxSize":"3000",
   "thumbSize":"800",
   "loginHistory":[
   {
      "time": "1411053987",      
      "location":"example-city"
   },
   {
      "time": "1411053988",      
      "location":"example-city-2"
   }
]}

The PHP so far:

$accountData = json_decode(file_get_contents("data.json"));
$newLoginHistory['time'] = "1411053989";
$newLoginHistory['location'] = "example-city-3";
array_push($accountData['loginHistory'],$newLoginHistory);
file_put_contents("data.json", json_encode($accountData));

I keep getting 'null' as the output for the "loginHistory" object upon saving the JSON file.

Answer 1

The problem is that json_decode doesn't return arrays by default, you have to enable this. See here: Cannot use object of type stdClass as array?

Anyway, just add a parameter to the first line and you're all good:

$accountData = json_decode(file_get_contents("data.json"), true);
$newLoginHistory['time'] = "1411053989";
$newLoginHistory['location'] = "example-city-3";
array_push($accountData['loginHistory'],$newLoginHistory);
file_put_contents("data.json", json_encode($accountData));

If you enabled PHP errors/warnings you would see it like this:

Fatal error: Cannot use object of type stdClass as array in test.php on line 6

Answer 2

$accountData is an object, as it should be. Array access is not valid:

array_push($accountData->loginHistory, $newLoginHistory);
// or simply
$accountData->loginHistory[] = $newLoginHistory;

Answer 3

This is a small and simple guide on how to modify a JSON file with PHP.

//Load the file
$contents = file_get_contents('data.json');

//Decode the JSON data into a PHP array.
$contentsDecoded = json_decode($contents, true);

//Create a new History Content.
$newContent = [
  'time'=> "1411053989",
  'location'=> "example-city-3";
]

//Add the new content data.
$contentsDecoded['loginHistory'][] = $newContent;


//Encode the array back into a JSON string.
$json = json_encode($contentsDecoded);

//Save the file.
file_put_contents('data.json', $json);

A step-by-step explanation of the code above.

1. We loaded the contents of our file. At this stage, it is a string that contains JSON data.

2. We decoded the string into an associative PHP array by using the function json_decode. This allows us to modify the data.

3. We added new content to contentsDecoded variable.

4. We encoded the PHP array back into a JSON string using json_encode.

5. Finally, we modified our file by replacing the old contents of our file with the newly-created JSON string.