Post request not reaching server from iOS device

Question

Trying to make simple post request to a remote PHP file. I'm not receiving the parameters on the server. Which I receive using Postman Btw. So the service seems ok. Something seems to be missing the iOS code here.

- (void) sendPostRequest {
NSError *error;

NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
NSURL *url = [NSURL URLWithString:baseURLPost];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request addValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[request addValue:@"application/json" forHTTPHeaderField:@"Accept"];

[request setHTTPMethod:@"POST"];
NSDictionary *mapData = [[NSDictionary alloc] initWithObjectsAndKeys:
                         @"JSON", @"responseType",
                         [UserManager sharedInstance].user.username, @"username",
                            self.textView.text, @"text",
                         nil];

NSData *postData = [NSJSONSerialization dataWithJSONObject:mapData options:0 error:&error];
allowLossyConversion:YES];
[request setHTTPBody:postData];
[[session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    if (error) {
        NSLog(@"%@", [error.userInfo valueForKey:@"NSDebugDescription"]);
    } else {
       NSArray *jsonResponseArray = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
        NSLog(@"%@", jsonResponseArray);
    }
}] resume];
}

My PHP code to receive post REquest.

<?php
header("Content-type:application/json");

$postText= $_POST['text'];
$username = $_POST['username'];
$itemType = $_POST['itemType'];
$responseType = $_POST['responseType'];
$pictureLink = $_POST['pictureLink'];
$timestamp = $_POST['timestamp'];
$tags = $_POST['tags'];

if($timestamp==null){
    $timestamp = date('Y-m-d G:i:s');
}
$arr = array('username' => $username);
echo json_encode($arr);
?>

The jsonResponseArray from this is username = "<null>";

Answer 1

Use

$handle = fopen('php://input','r'); 
$jsonInput = fgets($handle); 

instead of $_POST

Like this:

<?php
    header("Content-type:application/json");

$handle = fopen('php://input','r');
$jsonInput = fgets($handle);
$arr = json_decode($jsonInput, true);

$postText= $arr['text'];
$username = $arr['username'];
$itemType = $arr['itemType'];
$responseType = $arr['responseType'];
$pictureLink = $arr['pictureLink'];
$timestamp = $arr['timestamp'];
$tags = $arr['tags'];

if($timestamp==null){
    $timestamp = date('Y-m-d G:i:s');
}
$arr = array('username' => $username);
echo json_encode($arr);
?>