Json file replaces the data instead of adding - php

Question

I have a Json file which i'm using for my website, however when I fill out the form and send it over to my Json file it somehow replaces the old data with the new one instead of adding it with an increment.
my json/php set-up:
$id = '';
if(isset($_POST['submit'])) {
if(file_exists('json_files/database.json')) {
$current_data = file_get_contents('json_files/database.json');
$array_data = json_decode($current_data, true);
$last_item = end($array_data);
$last_item_id = $last_item['id'];
$arrExercise = array(
'id' => ++$last_item_id,
'exerciseTitle' => $Title,
'exerciseWord' => $question_takeAudio_exerciseWord,
'syllables' => $Syllables
);
$array_data[] = $extra;
$final_data = json_encode($array_data, JSON_PRETTY_PRINT);
if(file_put_contents('json_files/database.json', $final_data)) {
header("Location: exercise_CMS.php");
} else {
echo "Oopsie! Something went wrong!";
exit();
}
}
}
my json:
{
"id": 1,
"exerciseTitle": "Huisss",
"exerciseWord": [
"Huisarts"
],
"syllables": [
"Huis",
"arts"
]
}
now, if I would fill out my form again, the above would be REPLACED for the new data send over to my json file. I want it however, to add it underneath with the increment of +1. Am I missing out on something?
EDIT: the json/php set-up has been updated. but most likely I am still missing parts out because now it returns a "0 null" value. however it doesn't overwrite the old data.

Answer 1

The default behavior of file_put_contents is to replace the file. According to the docs, "the existing file is overwritten, unless the FILE_APPEND flag is set."
However, as #deceze pointed out, you don't actually want to append to your JSON file because it won't be valid JSON. You'll need to read in your existing JSON file, update it and then overwrite. You'll also need to add your objects to a top level array like this:
{
"exercises": []
}