users.php

<?php declare(strict_types=1);

if (!isset($_POST['login-submit'])) {
    header("Location: ../index.php");
    exit();
}

require 'dbh.inc.php';

$mailuid = $_POST['mailuid'] ?? null;
$password = $_POST['pwd'] ?? null;

if (empty($mailuid) ||  empty($password)) {
    header("Location: ../index.php?error=emptyfields");
    exit();
}
$sql = "SELECT * FROM users WHERE uidUsers=? OR emailUsers=?;";
$stmt = mysqli_stmt_init($conn);
if (!mysqli_stmt_prepare($stmt, $sql)) {
    header("Location: ../index.php?error=sqlerror");
    exit();
}
mysqli_stmt_bind_param($stmt, "ss", $mailuid, $mailuid);
mysqli_stmt_execute($stmt);
$result = mysqli_stmt_get_result($stmt);
if (!$row = mysqli_fetch_assoc($result)) {
    header("Location: ../index.php?error=nouser");
    exit();
}
$pwdCheck = password_verify($password, $row['pwdUsers']);
if ($pwdCheck == false) {
    header("Location: ../index.php?error=wrongpwd");
    exit();
}
session_start();
$_SESSION['userId'] = $row['idUsers'];
$_SESSION['userUid'] = $row['uidUsers'];

header("Location: ../index.php?login=success");
exit();