how do i resolve this error - Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result [duplicate]

how do i resolve this error in php - Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result. i'm trying to create login and sign-up pages for my project, the form is handled by one php file auth-controller, this is the code below;

<?php
use PHPMailer\PHPMailer\PHPMailer;
session_start();
$username = "";
$email = "";
$errors = [];

$conn = new mysqli('localhost', 'id14612068_topadmin', 'Ju<|2<!PUsS{#PE', 'id14612068_topguild');

// SIGN UP USER
if (isset($_POST['signup-btn'])) {
    if (empty($_POST['username'])) {
        $errors['username'] = 'Username required';
    }
    if (empty($_POST['email'])) {
        $errors['email'] = 'Email required';
    }
    if (empty($_POST['password'])) {
        $errors['password'] = 'Password required';
    }
    if (isset($_POST['password']) && $_POST['password'] !== $_POST['passwordConf']) {
        $errors['passwordConf'] = 'The two passwords do not match';
    }

    $username = $_POST['username'];
    $email = $_POST['email'];
    $token = bin2hex(random_bytes(50)); // generate unique token
    $password = password_hash($_POST['password'], PASSWORD_DEFAULT); //encrypt password

    // Check if email already exists
    $sql = "SELECT * FROM users WHERE email='$email' LIMIT 1";
    $result = mysqli_query($conn, $sql);
    if (mysqli_num_rows($result) > 0) {
        $errors['email'] = "Email already exists";
    }

    if (count($errors) === 0) {
  
        $emailtoken = "poiuztrewqasdfghjklmnbvcxy1234567890";
        $emailtoken = str_shuffle($emailtoken);
        $emailtoken = substr($emailtoken, 0, 10);
        
        $query = "INSERT INTO users SET username=?, email=?, token=?, password=?, emailToken=?";
        $stmt = $conn->prepare($query);
        $stmt->bind_param('sssss', $username, $email, $token, $password, $emailtoken);
        $result = $stmt->execute();
        require_once "PHPMailer/PHPMailer.php";
        require_once "PHPMailer/Exception.php";

        $mail = new PHPMailer();
        $mail->addAddress($email);
        $mail->setFrom("mayjriffs97@gmail.com", "mayor1997j");
        $mail->Subject = "Reset Password";
        $mail->isHTML(true);
        $mail->Body = "
                    Hi,<br><br>
                    
                    please click on the link below to verify your email:<br>
                    <a href='localhost/Confirm-Email.php?email=$email&token=$emailtoken'>click here</a><br><br>
                    
                    Kind Regards,<br>
                    My Name
                ";
         if (!$mail->send()) {
          echo  "ERROR: " . $mail->ErrorInfo;
         } else {
             echo "<h3 class='text-capitalise text-primary'>Please Check your Email Inbox for the link to reset your Password</h3>";
           }

        if ($result) {
            $user_id = $stmt->insert_id;
            $stmt->close();

            // TO DO: send verification email to user
             //sendVerificationEmail($email, $token);

            $_SESSION['id'] = $user_id;
            $_SESSION['username'] = $username;
            $_SESSION['email'] = $email;
            $_SESSION['verified'] = false;
            $_SESSION['message'] = 'You are registered, please confirm your email address to login!';
            $_SESSION['type'] = 'alert-success';
            header('location: login.php');
        } else {
            $_SESSION['error_msg'] = "Database error: Could not register user";
        }
    }
}

// LOGIN
if (isset($_POST['login-btn'])) {
    if (empty($_POST['username'])) {
        $errors['username'] = 'Username or email required';
    }
    if (empty($_POST['password'])) {
        $errors['password'] = 'Password required';
    }
    $username = $_POST['username'];
    $password = $_POST['password'];

    $sql = "SELECT * FROM users WHERE username='$username' LIMIT 1";
    $result = mysqli_query($conn, $sql);
    $emailcheck = mysqli_fetch_assoc($result);
    mysqli_free_result($result);

    if($emailcheck['isEmailConfirmed'] == 1){

        if (count($errors) === 0) {
            $query = "SELECT * FROM users WHERE username=? OR email=? LIMIT 1";
            $stmt = $conn->prepare($query);
            $stmt->bind_param('ss', $username, $password);
    
            if ($stmt->execute()) {
                $result = $stmt->get_result();
                $user = $result->fetch_assoc();
                if (password_verify($password, $user['password'])) { // if password matches
                    $stmt->close();
    
                    $_SESSION['id'] = $user['id'];
                    $_SESSION['username'] = $user['username'];
                    $_SESSION['email'] = $user['email'];
                    $_SESSION['verified'] = $user['verified'];
                    $_SESSION['message'] = 'You are logged in!';
                    $_SESSION['type'] = 'alert-success';
                    header('location: app/index.php');
                    exit(0);
                } else { // if password does not match
                    $errors['login_fail'] = "Wrong username / password";
                }
            } else {
                $_SESSION['message'] = "Database error. Login failed!";
                $_SESSION['type'] = "alert-danger";
            }
        }

    }else{
        $errors['Confirm_Email_Failed'] = "You have not confirmed your email <br> Please confirm your email to login";
    }
}

everything seems to be working perfectly on the local server, but when i try to sign-up or login into the project on the live server, i get an error on this line -

$sql = "SELECT * FROM users WHERE email='$email' LIMIT 1";
    $result = mysqli_query($conn, $sql);
    if (mysqli_num_rows($result) > 0) {
        $errors['email'] = "Email already exists";
    }

how can i fix this please