takin null all the time PHP - php

Question

I am really beginner on PHP and Android and I can't find the problem.
Here is the by return book PHP code.
Firstly it takes two variables Id and id. It selects id from Books database if the id matches it store the Books database variables.
If takenby === Id it should assign true to $success, otherwise it should assign false to $success but every time $success is null.
I don't understand why it is always null.
Thank for your answering...
<?php
$con = mysqli_connect("localHost","name","password","database");
$id = $_POST["id"];
$Id = $_POST["Id"];
if (mysqli_connect_errno($con))
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
mysqli_set_charset($con, 'utf8');
$statement2 = mysqli_prepare($con, "SELECT * FROM Books WHERE id = ?");
mysqli_stmt_bind_param($statement2,"s" , $id);
mysqli_stmt_execute($statement2);
mysqli_stmt_store_result($statement2);
mysqli_stmt_bind_result($statement2, $name, $author, $ıd, $date, $takenby);
$response = array();
$response["success"] = false;
if($takenby===$Id)
{
$statement = mysqli_prepare($con,"UPDATE Books SET takenby = '' , date = '' WHERE id = ?");
mysqli_stmt_bind_param($statement,"s" , $id);
$success = mysqli_stmt_execute($statement);
}
$response = array();
$response["success"]=$success;
$response["id"] = $id;
//json data formatı
echo json_encode($response);
mysqli_close($con);
?>
Here is the console output,
Value null at success of type org.json.JSONObject$1 cannot be converted to boolean.

Answer 1

The problem is in that script is missing the fetch part. After I realized that fetch is missing, and I fetch statement.
Here is some example from PHP documentation about fetch
<?php
$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();
/* Fetch all of the remaining rows in the result set */
print("Fetch all of the remaining rows in the result set:\n");
$result = $sth->fetchAll();
print_r($result);
?> [1]
If someone encounters some kind of problem, ı hope that it would help.
[1] http://php.net/manual/en/pdostatement.fetchall.php