submitting login and sign up forms using ajax

1<?php
2
3session_start();
4
5  // check whether the loginbtn was clicked
6if (isset($_POST['loginbtn'])) {
7
8  include_once 'dbh.inc.php';
9
10    // initialize variable
11  $uid = trim($_POST['uid']);
12  $pwd = trim($_POST['pwd']);
13
14    // error handlers
15
16    // check if inputs are empty
17  if (empty($uid) || empty($pwd)) {
18
19    $conn = null;
20    header("Location: ../index.php?login=error_field");
21    exit();
22
23  } else {
24
25      // check if username is in database
26    $stmt = $conn->prepare("SELECT user_uid FROM users WHERE user_uid = ?");
27    $stmt->execute([$uid]);
28
29    if ($stmt->rowCount() < 1) {
30
31      $conn = null;
32      header("Location: ../index.php?login=error_username");
33      exit();
34
35    } else {
36
37        // check if password is correct
38      $stmt = $conn->prepare("SELECT user_pwd FROM users WHERE user_uid = ?");
39      $stmt->execute([$uid]);
40      $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
41
42        // dehashing the password
43      $hashedPwdCheck = password_verify($pwd, $result[0]['user_pwd']);
44
45      if ($hashedPwdCheck == false) {
46
47        $conn = null;
48        header("Location: ../index.php?login=error_password");
49        exit();
50
51      } else {
52
53          // login the user in
54        $stmt = $conn->prepare("SELECT user_id, user_first, user_last, user_email, user_uid FROM users WHERE user_uid = ?");
55        $stmt->execute([$uid]);
56        $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
57
58        $_SESSION['user_id'] = $result[0]['user_id'];
59        $_SESSION['user_first'] = $result[0]['user_first'];
60        $_SESSION['user_last'] = $result[0]['user_last'];
61        $_SESSION['user_email'] = $result[0]['user_email'];
62        $_SESSION['user_uid'] = $result[0]['user_uid'];
63
64        $conn = null;
65        header("Location: ../updates.php?login=success");
66        exit();
67
68      }
69
70    }
71
72  }
73
74} else {
75
76  header("Location: ../index.php?login=error");
77  exit();
78
79}
80
81?>
82