Building a response array after binding parameters for PDO - php

Question

I am trying to build the array that will return to my ajax success. How do I build the array after binding it to something like :some variable.
The following script runs to completion, and inserts with no problem into sql. But the variables comment and transaction come back as null in the response. I think the problem is using $comment and $transaction when building the array. What is the right way to reference these values in the array?
require('../dbcon2.php');
//Connection 1
try {
$conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $conn->prepare("UPDATE listings SET comment = :comment, transaction = :transaction, ad_link = :ad_link WHERE id = :id");
// Bind
$stmt->bindParam(':id', $_POST['id']);
$stmt->bindParam(':comment', $_POST['comment']);
$stmt->bindParam(':transaction', $_POST['transaction']);
$stmt->execute();
// Build array
$response = array
('state' => 200, "success" => true, "id" => ':id', "comment" => $comment, "transaction" => $transaction
);
exit(json_encode($response));
}
catch (Exception $e) {
// create a asociative array
$data = array("success" => false, "sentence" => $sql, "error" => $e.getMessage());
// encode data and exit.
exit(json_encode($data));
}

Answer 1

As per OP's wish:
Do as you did for "id" => ':id'
"id" => ':id', "comment" => ':comment', "transaction" => ':transaction'
Plus, quoting Jeroen (kudos to)
Why don't you use the $_POST variable? That contains the values you need and you use them already in your database query.

Answer 2

You can't retrieve bound values after calling ->bindParam(); also, the variables $comment and $transaction aren't defined (unless you set them yourself or when using voodoo php settings).
That said, you already know those values:
$response = array(
'state' => 200,
"success" => true,
"id" => $_POST['id'],
"comment" => $_POST['comment'],
"transaction" => $_POST['transaction'],
);
Btw, in the exception branch you have a small bug:
$data = array("success" => false, "sentence" => $sql, "error" => $e.getMessage());
^
You should use $e->getMessage() instead.