mysqli 준비된 명령문이 실패하는 이유는 무엇이며 매개변수를 올바르게 바인딩하려면 어떻게 해야 합니까?

$name = 'one';
$age = 1;

$stmt = $mysqli->prepare("INSERT INTO users (name, age) VALUES (?,?)");

// Bind parameters (typehint: string, integer)
$stmt->bind_param('si', $name, $age);

// Now you can execute
$stmt->execute();

$mysqli = new mysqli("localhost", "root", "root", "test");
if ($mysqli->connect_errno) {
    echo "Connection failed: " . $mysqli->connect_error;
}

$stmt = $mysqli->prepare("INSERT INTO users (name, age) VALUES (?,?)");

// Bind parameters (typehint: string, integer)
$stmt->bind_param('si', $name, $age);

// Insert row
$stmt->execute();

$stmt = $mysqli->prepare("SELECT * FROM users WHERE name = ?");
$stmt->bind_param('s', $name);

$stmt->execute();

if ($stmt->errno) {
    echo "Error: " . $stmt->error;
} else {
    $result = $stmt->get_result();
}

// Process result