function for registering a user in php code example

Example 1: php user login and registration

<?php
session_start();

// initializing variables
$username = "";
$email    = "";
$errors = array(); 

// connect to the database
$db = mysqli_connect('localhost', 'root', '', 'registration');

// REGISTER USER
if (isset($_POST['reg_user'])) {
  // receive all input values from the form
  $username = mysqli_real_escape_string($db, $_POST['username']);
  $email = mysqli_real_escape_string($db, $_POST['email']);
  $password_1 = mysqli_real_escape_string($db, $_POST['password_1']);
  $password_2 = mysqli_real_escape_string($db, $_POST['password_2']);

  // form validation: ensure that the form is correctly filled ...
  // by adding (array_push()) corresponding error unto $errors array
  if (empty($username)) { array_push($errors, "Username is required"); }
  if (empty($email)) { array_push($errors, "Email is required"); }
  if (empty($password_1)) { array_push($errors, "Password is required"); }
  if ($password_1 != $password_2) {
	array_push($errors, "The two passwords do not match");
  }

  // first check the database to make sure 
  // a user does not already exist with the same username and/or email
  $user_check_query = "SELECT * FROM users WHERE username='$username' OR email='$email' LIMIT 1";
  $result = mysqli_query($db, $user_check_query);
  $user = mysqli_fetch_assoc($result);
  
  if ($user) { // if user exists
    if ($user['username'] === $username) {
      array_push($errors, "Username already exists");
    }

    if ($user['email'] === $email) {
      array_push($errors, "email already exists");
    }
  }

  // Finally, register user if there are no errors in the form
  if (count($errors) == 0) {
  	$password = md5($password_1);//encrypt the password before saving in the database

  	$query = "INSERT INTO users (username, email, password) 
  			  VALUES('$username', '$email', '$password')";
  	mysqli_query($db, $query);
  	$_SESSION['username'] = $username;
  	$_SESSION['success'] = "You are now logged in";
  	header('location: index.php');
  }
}

// ...

Example 2: php code for activating login page

<?php
        if (! empty($response)) {
            ?>
<div id="response" class="<?php echo $response["type"]; ?>
    ">
    <?php echo $response["message"]; ?>
</div>
<?php
        }
        ?>
<form action="" method="POST" onsubmit="return signupvalidation()">
    <div class="row">
        <label>Name</label><span id="name_error"></span>
        <div>
            <input type="text" class="form-control" name="name"
                id="name" placeholder="Enter your name">

        </div>
    </div>

    <div class="row">
        <label>Email</label><span id="email_error"></span>
        <div>
            <input type="text" name="email" id="email"
                class="form-control" placeholder="Enter your Email ID">

        </div>
    </div>

    <div class="row">
        <label>Password</label><span id="password_error"></span>
        <div>
            <input type="Password" name="password" id="password"
                class="form-control" placeholder="Enter your password">

        </div>
    </div>

    <div class="row">
        <label>Confirm Password</label><span id="confirm_password_error"></span>
        <div>
            <input type="password" name="confirm_pasword"
                id="confirm_pasword" class="form-control"
                placeholder="Re-enter your password">

        </div>
    </div>

    <div class="row">
        <div align="center">
            <button type="submit" name="submit" class="btn signup">Sign
                Up</button>
        </div>
    </div>

<div class="row">
    <div>
        <a href="login.php"><button type="button" name="submit"
                class="btn login">Login</button></a>
    </div>
</div>

</form>