PHP, split received POST data after few words or sentences - php

Question

I am able to send JSONObject data from my application to server with PHP. I am also able to read the data. But now I want to send the data with a USER ID and type of data in the first two sentences. I am able to send this data from my application.
But I am not experienced with working on PHP and I dont know how to split this data after reading USER id and the type I have received and to store the rest of data separately ( and should be stored as json data with USER ID as filename).
Currently I am using the following to just save the
<?php
$content = file_get_contents('php://input');
$data = json_decode($content, true);
$fp = fopen('results.json', 'w');
fwrite($fp, json_encode($data));
fclose($fp);
if(!is_array($data)){
throw new Exception('Received content contained invalid JSON!');
}
echo "Data Received";
?>
This is the json data format,
[{ "increment_id": "1", "uuid": "43c87b6e-4fd5-4f1b-9bba-3e512eb4787a", "xValue": "39.0", "yValue": "72.0", "inputTime": "Thu Mar 08 15:38:58" }]
I also want to attach user id with it, which I am able to attach and send it to server, but I cannot use json decode now as the format changes to re encode if I give a userid with it in the first sentence . So after attaching userid and type the data looks like this
UserID Type [{ "increment_id": "1", "uuid": "43c87b6e-4fd5-4f1b-9bba-3e512eb4787a", "xValue": "39.0", "yValue": "72.0", "inputTime": "Thu Mar 08 15:38:58" }]

Answer 1

What sentences? Send it where? Its far from clear what you are asking.
I dont know how to split this data
We don't either. What do you mean by split? That implies there's going to more than one data item - where do you want to split it? What do you want to do with the 2 parts?
should be stored as json data with USER ID as filename
It is very unlikely that it should be stored where you are currently putting it - particularly when you are applying no validation to the data you saved.
Consider (and note the differences with your script):
<?php
define("DEST_DIR", "/not/in/your/document/root/");
$content = file_get_contents('php://input');
$data = json_decode($content, true);
if (isset($data['USER'])) {
$filename=basename($data['USER']);
$filename="data_" . array_shift(explode('.', $filename) . 'json';
file_put_contents(DEST_DIR . $filename);
print json_encode(array('result'=>'success'));
} else {
header("Bad Request", true, 400);
print json_encode(array('result'=>'bad input data');
}