A simple wordpress plugin to login with only phone number

phone-only-login.php

<?php
/**
 * Plugin Name: Phone Only Login
 */

function generateRandomString($length = 10)
{
    $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $charactersLength = strlen($characters);
    $randomString = '';
    for ($i = 0;$i < $length;$i++)
    {
        $randomString .= $characters[rand(0, $charactersLength - 1) ];
    }
    return $randomString;
}

// Registration Form Shortcode
function registration_form_fn()
{
    if (is_user_logged_in())
    {
        echo 'User already logged in';
    }
    else
    {
        if ($_POST['email'] && $_POST['phone'])
        {
            $email = htmlspecialchars($_POST['email']);
            $phone = htmlspecialchars($_POST['phone']);
            $password = generateRandomString();
            if (username_exists($phone) || email_exists($email))
            {
                echo 'Already Registered';
            }
            else
            {
                $userdata = array(
                    'user_login' => $phone,
                    'user_email' => $email,
                    'user_pass' => $password
                );
                $user_id = wp_insert_user($userdata);
                if ($user_id)
                {
                    $updated = update_user_meta($user_id, 'saved_pword', $password);
                    echo 'User Registration Successfull';
                }
            }

        }
        else
        {
?>
<form method="post">
  <div class="form-group">
    <label for="InputEmail">Email address</label>
    <input name="email" type="email" class="form-control" id="InputEmail" placeholder="Enter email" required="required">
  </div>
  <div class="form-group">
    <label for="InputPhone">Phone Number</label>
    <input name="phone" type="text" class="form-control" id="InputPhone" placeholder="017....."  required="required">
  </div>
  <button type="submit" class="btn btn-primary">Submit</button>
</form>
 <?php
        }
    }
}
add_shortcode('registration_form', 'registration_form_fn');

// Login Form Shortcode
function login_form_fn()
{
    if (is_user_logged_in())
    {
        echo 'User already logged in';

    }
    else
    {
?>
<form method="post">
  <div class="form-group">
    <label for="InputPhone">Phone Number</label>
    <input name="ephone" type="text" class="form-control" id="InputPhone" placeholder="017....."  required="required">
  </div>
  <button type="submit" class="btn btn-primary">Login</button>
</form>
<?php
    }
}
add_shortcode('login_form', 'login_form_fn');

/**
 * Perform automatic login.
 */
function wpdocs_custom_login()
{

    if ($_POST['ephone'])
    {
        $phone = htmlspecialchars($_POST['ephone']);
        $user = get_user_by('login', $phone);
        if ($user)
        {
            $user_id = $user->ID;
            $password = get_user_meta($user_id, 'saved_pword', true);

            if ($password)
            {

                $creds = array(
                    'user_login' => $phone,
                    'user_password' => $password,
                    'remember' => true
                );

                $user = wp_signon($creds, false);

                if (is_wp_error($user))
                {
                    echo $user->get_error_message();
                }
                else
                {
                    wp_redirect(home_url());
                    exit;
                }

            }
        } else {
        	echo 'Wrong Phone Number';
        }
    }
}

// Run before the headers and cookies are sent.
add_action('after_setup_theme', 'wpdocs_custom_login');