Overwrite JSON if fields match PHP - php

Question

I'm trying to write to a json file, and want to be able to overwrite an object if certain fields match. Right now, I have code that gets whats currently in the JSON file, but that just adds the latest object to the end of it. What I need to do is that if the message fields match, then I need to replace the entry with the newer one. Know what I mean?
Thanks for the help!
PHP:
$file = file_get_contents('test.json');
$data = json_decode($file);
unset($file);//prevent memory leaks for large json.
//insert data here
$data[] = array("message" => $name, "latitude" => $lat, "longitude" => $lon, "it" => $it);
//save the file
file_put_contents('test.json',json_encode($data));
echo json_encode($data);
unset($data);//release memory

Answer 1

You can use array_filter to find the element with the matching name and update it in place. This will not remove any existing duplicates for you, though.
$datum = array_filter($data, function (&$elem) use ($name, $lat, $lon, $it) {
if ($elem['message'] === $name) {
$elem = array('message' => $name /* snip */)
return true;
}
});
if (!$datum) { /* append array */ }

Answer 2

assuming I understand correctly, you only need to check if two elements in your $data array are equal, based on the message. Easiest way to do that is use the key of the data array, and reset it afterwards. so something similar to :
$file = file_get_contents('test.json');
$data = json_decode($file);
unset($file);//prevent memory leaks for large json.
//insert data here
$data[$message] = array("message" => $name, "latitude" => $lat, "longitude" => $lon, "it" => $it);
//save the file
$data = array_values($data);
file_put_contents('test.json',json_encode($data));
echo json_encode($data);
unset($data);//release memory
this will increase memory consumption, so you can use md5() for the keys instead to keep it low.

Answer 3

If you use json_decode($string, true), you will get either an associative or numeric array. This array can be manipulated with standard php array methods.
$array = json_decode($string, true);
if(md5($data['message']) != md5($newMessage)) {
$array['message'] = $newMessage;
}
I used an md5, because i don't know how the message is structured.