注册脚本问题

Question

Im trying to create a register script. This is my first time trying to create a secure register page using functions in php. The issue i get is with the error "Database Error line 55 " and "Database error line 39" I followed an example from the internet but am not quite sure why im getting the errors.

Heres the code:

register.inc.php:

Register.inc.php

<?php
include_once 'db_connect.php';
include_once 'connection.php';

$error_msg = "";

if (isset($_POST['username'], $_POST['email'], $_POST['p'])) {
// Sanitize and validate the data passed in
$username = filter_input(INPUT_POST, 'username', FILTER_SANITIZE_STRING);
$email = filter_input(INPUT_POST, 'email', FILTER_SANITIZE_EMAIL);
$email = filter_var($email, FILTER_VALIDATE_EMAIL);
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    // Not a valid email
    $error_msg .= '<p class="error">The email address you entered is not valid</p>';
 }

$password = filter_input(INPUT_POST, 'p', FILTER_SANITIZE_STRING);
if (strlen($password) != 128) {
    // The hashed pwd should be 128 characters long.
    // If it's not, something really odd has happened
    $error_msg .= '<p class="error">Invalid password configuration.</p>';
 }

// Username validity and password validity have been checked client side.
// This should should be adequate as nobody gains any advantage from
// breaking these rules.
//

$prep_stmt = "SELECT id FROM members WHERE email = ? LIMIT 1";
$stmt = $mysqli->prepare($prep_stmt);

   // check existing email  
if ($stmt) {
    $stmt->bind_param('s', $email);
    $stmt->execute();
    $stmt->store_result();

    if ($stmt->num_rows == 1) {
        // A user with this email address already exists
        $error_msg .= '<p class="error">A user with this email address already exists.</p>';
                    $stmt->close();
    }
            $stmt->close();
} else {
    $error_msg .= '<p class="error">Database error Line 39</p>';
            //$stmt->close();
}

// check existing username
$prep_stmt = "SELECT id FROM members WHERE username = ? LIMIT 1";
$stmt = $mysqli->prepare($prep_stmt);

if ($stmt) {
    $stmt->bind_param('s', $username);
    $stmt->execute();
    $stmt->store_result();

            if ($stmt->num_rows == 1) {
                    // A user with this username already exists
                    $error_msg .= '<p class="error">A user with this username already     
exists</p>';
                    $stmt->close();
            }
            $stmt->close();
    } else {
            $error_msg .= '<p class="error">Database error line 55</p>';
            //$stmt->close();
    }

// TODO: 
// We'll also have to account for the situation where the user doesn't have
// rights to do registration, by checking what type of user is attempting to
// perform the operation.

if (empty($error_msg)) {
    // Create a random salt
    //$random_salt = hash('sha512', uniqid(openssl_random_pseudo_bytes(16), TRUE)); // Did not      
    work
    $random_salt = hash('sha512', uniqid(mt_rand(1, mt_getrandmax()), true));

    // Create salted password 
    $password = hash('sha512', $password . $random_salt);

    // Insert the new user into the database 
    if ($insert_stmt = $mysqli->prepare("INSERT INTO members (username, email, password, salt)         
    VALUES (?, ?, ?, ?)")) {
        $insert_stmt->bind_param('ssss', $username, $email, $password, $random_salt);
        // Execute the prepared query.
        if (! $insert_stmt->execute()) {
            header('Location: ../error.php?err=Registration failure: INSERT');
        }
    }
    header('Location: ./register_success.php');
}
}