JSON/CURL issue - php

Question

My CURL request takes in two variables as shown below:
<?php
$id = $_GET["id"];
$review = $_GET["review"];
$url = 'http://edward/~treeves/ratingJSON.php';
$jsonData = array("id" => "$id", "review" => "$review");
$ch = curl_init($url);
$jsonDataEncoded = json_encode($jsonData);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, array('json' => $jsonDataEncoded));
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
$result = curl_exec($ch);
?>
And posts it to the web service shown below:
<?php
header("Content-type: application/json");
try {
$conn = new PDO("mysql:host=localhost;dbname=treeves;", "treeves", "oopheiye");
$json = $_POST["json"];
$data = json_decode ($json, true);
$result = $conn->query("INSERT INTO poi_reviews (poi_id, review)
VALUES ('$data[ID]', '$data[review]')");
} catch (Exception $e) {
echo $e->getMessage();
}
?>
However the data being inserted is blank. When I use var_dump($data) on the web service is shows 1 NULL. I think it's to do with the variables in the CURL file as the web service works. Any ideas?
Update
Taking out the HTTP header and using 'var_dump($data, $error === JSON_ERROR_UTF8)' is returning the following:
array(2) { ["id"]=> string(4) "1014" ["review"]=> string(1) "2" } bool(false)

Answer 1

Here you set up form encoded data with one key (json) that has a value (of JSON encoded data):
curl_setopt($ch, CURLOPT_POSTFIELDS, array('json' => $jsonDataEncoded));
Here you tell the server that you are sending JSON and not form encoded data.
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
One of the above has to be wrong, since they are contradictory.
Here you try to read form encoded data:
$_POST["json"];
So claiming you are sending plain JSON is wrong (your JSON is encapsulated in form encoding).
Remove this line:
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));