update json replacing variable input from form in php - php

Question

Greeting, I'm new to PHP, and currently looking for a way to edit json.
I have a form to input the key that wants to edit. I echo the input from form and successfully got the output showing but it didn't pass to json file to update. The code is as below.
function testfun()
{
// read file
$data = file_get_contents('Book2.json');
// decode json to array
$json_arr = json_decode($data, true);
foreach ($json_arr as $key => $value) {
if ($value['CELL_NAME'] == $_POST['in_cell']) {
$json_arr[$key]['#25'] = $_POST['in_remark'];
}
}
// encode array to json and save to file
file_put_contents('Book2.json', json_encode($json_arr));
}
//you this post contain test?
//test is the the button when i submit the form
if (array_key_exists('test',$_POST))
{
testfun();
}
Am I missing something?

Answer 1

Try my code.
function testfun()
{
// read file
$data = file_get_contents('Book2.json');
// decode json to array
$json_arr = array(json_decode($data, true));
foreach ($json_arr as $key => $value) {
if ($value['CELL_NAME'] == $_POST['in_cell']) {
$json_arr[$key]['#25'] = $_POST['in_remark'];
}
}
// encode array to json and save to file
file_put_contents('Book2.json', json_encode($json_arr));
}
if (array_key_exists('test',$_POST))
{
testfun();
}

Answer 2

As you mention in the comments, the content of the $json_arr is:
{"CELL_NAME":"1234A","#25":"remark value"}
So when you trying to access in:
foreach ($json_arr as $key => $value) {
if ($value['CELL_NAME'] == $_POST['in_cell']) {
$json_arr[$key]['#25'] = $_POST['in_remark'];
}
}
it has no key for $value at CELL_NAME key.
I guess your $data from the file should be like that (an array of JSONs):
$data = '[{"CELL_NAME":"1234A","#25":"remark value"}, {"CELL_NAME":"1234B","#25":"remark value"}]';
Now you can do this and it will work:
$arr = json_decode($data, true);
foreach ($arr as $key => $value) {
if ($value['CELL_NAME'] == "1234A") // you can change with $_POST['in_cell']
$arr[$key]['#25'] = "test"; // you can change with $_POST['in_remark']
}