Call to a member function bind_Param() in get method - php

Question

I wonder whats the problem in my code? I tried all the sources I can search but it still gives me the same error which is still "Call to a member function bind_Param() on a non-object".here's my code.,hope someone can help me, thanks
$app->get('/students/:student_id',function () use($app){
$sql = "SELECT * FROM students WHERE student_id =:student_id";
try {
$db = connect_db();
$stmt = $db->prepare($sql);
$stmt->bind_Param("student_id", $student_id);
$stmt->execute();
$students = $stmt->fetchObject();
$db = null;
echo json_encode($students);
}
catch(PDOException $e) {
echo '{"error":{"text":'. $e->getMessage() .'}}';
}
});

Answer 1

This one works:
$app->get('/students/:student_id', function ($student_id) use($app){
$sql = "SELECT * FROM students WHERE student_id = ?";
try {
$db = connect_db();
$stmt = $db->prepare($sql);
$stmt->bind_Param("i", $student_id);
$stmt->execute();
$result = $stmt->get_result();
$students = $result->fetch_object();
$db = null;
echo json_encode($students);
}
catch(PDOException $e) {
echo '{"error":{"text":'. $e->getMessage() .'}}';
}
});
I assume that you're using this definition of the connect_db function:
function connect_db() {
$dbhost="localhost";
$dbuser="user";
$dbpass="pass";
$dbname="stackoverflow-33750846";
return new mysqli($dbhost, $dbuser, $dbpass, $dbname);;
}
Perhaps there is a bit of confusion using the database connection and read data from it, so I add some points:
Be sure to pass $student_id as a parameter to the callable function;
$stmt->bind_Param accepts a string that represents the type of the parameters and all the binding parameters;
fetchObject is a function of the mysqli_result class.