SQL Login System - php

Question

I coded this login system, but whenever I try to log in with the only username and password included in my database table, I get redirected to index.php?error=sqlerror. I checked the code for spelling mistakes but there are none. Could this be a problem with the database connection? I use MAMP. I have checked the database and it displays the Success message so it seems to be working. Do you know what I am doing wrong? Thank you!
DATABASE CONNECTION (file name: dbh.inc.php)
$servername = "127.0.0.1";
$dBUsername = "root";
$dBPassword = "";
$dBName = "gallerydatabase";
$conn = mysqli_connect($servername, $dBUsername, $dBPassword, $dBName);
if (!$conn) {
echo "Error: Unable to connect to MySQL.";
}
echo "Success";
mysqli_close($conn);
?>
LOG-IN PHP CODE (file name: login.inc.php)
if (isset($_POST['login-submit'])) {
require 'dbh.inc.php';
$mailuid = $_POST['mailuid'];
$password = $_POST['pwd'];
if (empty($mailuid) || empty($password)) {
header ("Location: ../index.php?error=emptyfields");
exit();
}
else {
$sql = "SELECT * FROM users WHERE uidUsers=?;";
$stmt = mysqli_stmt_init($conn);
if (!mysqli_stmt_prepare($stmt, $sql)) {
header ("Location: ../index.php?error=sqlerror");
exit();
}
else {
mysqli_stmt_bind_param($stmt, "s", $mailuid);
mysqli_stmt_execute($stmt);
$result = mysqli_stmt_get_result($stmt);
if ($row = mysqli_fetch_assoc($result)) {
$pwdCheck = password_verify($password, $row['pwdUsers']);
if ($pwdCheck == false) {
header ("Location: ../index.php?error=wrongpwd");
exit();
}
else if ($pwdCheck == true) {
session_start();
$_SESSION['userId'] = $row['idUsers'];
$_SESSION['userUid'] = $row['uidUsers'];
header ("Location: ../index.php?login=sucess");
exit();
}
else {
header ("Location: ../index.php?error=wrongpwd");
exit();
}
}
else {
header ("Location: ../index.php?error=nouser");
exit();
}
}
}
}
else {
header ("Location: ../index.php");
exit();
}

Answer 1

I think the problem is in your file dbh.inc.php, you create the connection $conn = mysqli_connect($servername, $dBUsername, $dBPassword, $dBName); and later you close it as well mysqli_close($conn);.
So by the time you come to use $conn in login.inc.php your connection is closed. What you need to do is write a function in dbh.inc.php that returns a live connection (don't call close), use that to do your DB queries / insert and after that close the connection.
A reusable database class can be written (functional style) as follows
<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
trait DBInfo {
protected $servername = "127.0.0.1";
protected $username = "root";
protected $password = "";
protected $dbname = "gallerydatabase";
}
class Database{
use DBInfo;
function __construct() {}
function connection(){
$conn = new mysqli($this->servername, $this->username,
$this->password, $this->dbname);
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
} else{
$conn->autocommit(FALSE);
return $conn;
}
}
function select($sql, $fn2bind_takestmt, $fn2process_row_return_result){
try{
$result = array();
$conn = $this->connection();
$stmt = $conn->prepare($sql);
$fn2bind_takestmt($stmt);
$stmt->execute();
$rowset = $stmt->get_result();
while ($row = $rowset->fetch_assoc()) {
$obj = $fn2process_row_return_result($row);
array_push($result, $obj);
}
}catch(Exception $e) {
$result = NULL;
throw $e;
}finally{
if(isset($rowset))$rowset->close();
if(isset($stmt))$stmt->close();
if(isset($conn))$conn->close();
}
return $result;
}
// You can introduce functions for insert, update and delete as well
}
?>
and then for database selects for example login check
<?php
function allow_login($user, $pwd){
$sql = "SELECT count(*) rec_count FROM users WHERE uidUsers=? and pwdUsers=?"
$db = new Database();
$result = $db->select($sql,
function($stmt) use($user, $pwd){
$stmt->bind_param("ss", $user, $pwd);
},
function($row){
if($row['rec_count'] > 0){// or whatever
return TRUE;
}
return FALSE;
}
);
if(isset($result)){
return $result[0];
}
return $result;
}
?>