unlink after file_put_contents - php

Question

I am trying to detect status of invoice from a json file, then if the status is a confirmed payment, update the status and write the json to a new location, then unlink the existing json location.
<?php
// get posted variables or die;
if (isset($_POST['num'])) {
$invoice = strip_tags($_POST['num']);
$filename = $invoice.'.json';
} else {
die;
}
if (isset($_POST['status'])) {
$status = strip_tags($_POST['status']);
} else {
die;
}
// get existing invoice
$content = file_get_contents('data/'.$invoice.'.json');
$data = json_decode($content, true);
// read json into variables
$email = $data['email'];
$id = $data['id'];
$addr = $data['tac_address'];
$os = $data['os'];
$exp = $data['experience'];
$hosting = $data['type'];
if (isset($data['telegram']) && $data['telegram'] != '') { $telegram = $data['telegram']; } else { $telegram = ''; }
if (isset($data['linkedin']) && $data['linkedin'] != '') { $linkedin = $data['linkedin']; } else { $linkedin = ''; }
if (isset($data['pay_status']) && $data['pay_status'] != '' && $data['pay_status'] == $status) { $status = $data['pay_status']; }
$payment_addr = $data['bitcoin'];
$payment_value = $data['value'];
$payment = substr($payment_value, 0, -4);
// turn variables into json array
$arr = array(
'id' => $invoice,
'email' => $email,
'tac_address' => $addr,
'os' => $os,
'experience' => $exp,
'type' => $hosting,
'telegram' => $telegram,
'linkedin' => $linkedin,
'bitcoin' => $payment_addr,
'value' => $payment_value,
'pay_status' => $status
);
$json = json_encode($arr);
// check status if paid save output to new location and delete old file
if ($status == 'Confirmed Payment') {
file_put_contents('paid_data/'.$filename, $json);
unlink('data/'.$filename);
}
The problem I am facing is that file_put_contents('paid_data/'.$filename, $json); ends up a file with a bunch of NULL variables. If I remove the unlink the variables save just fine, when I add it back the variables are all NULL.
So how can I verify file_put_contents takes place before the unlinking happens?
Also.... WHY does this happen? Isn't php supposed to be linear and shouldn't file_put_contents finish before the next line is carried out? Everything I have read about file_put_contents suggests as much. So why does the unlink take place before writing the content to a new location?

Answer 1

I still hope for a better answer, but so far this is my working solution to the problem. I changed the final if statement to the following. This seems to solve the issue - but there really has to be a better way than this. This feels very "hacky".
if ($status == 'Confirmed Payment') {
file_put_contents('paid_data/'.$filename, $json);
$i = 0;
while ($i < 1000) {
$i++;
if (file_exists('paid_data/'.$filename)) {
unlink('data/'.$filename);
break;
}
}
}

Answer 2

After mimicking your file structure and seeding a few examples, I was able to execute your code as is with the expected results. However, file_put_contents willreturn false on failure, so you might try something like this:
if ($status == 'Confirmed Payment') {
if(!file_put_contents('paid_data/'.$filename, $json);){
print_r(error_get_last());
die;
}
unlink('data/'.$filename);
}

Answer 3

Your code as originally written should be fine, as far as I can see. Usually when I see the kind of behavior you're describing, the problem is that the script itself is being called twice (or more) and overlapping calls are manipulating the same file.
I would definitely put in some debugging statements to verify this; I don't know your environment, but a simple line written to a log will probably be enlightening.