Need to Fix: Call to a member function real_escape_string()

I’ve created a login/register system in php, however I am receiving the call to member error, and Im unsure on how to fix it? I am simply trying to check that the password the user inputted into signup.php is the same as the hashed and original password in signup_user.php.

Here is my code:

sigin.php
<?php
ini_set("display_errors", "1");
ini_set("display_startup_errors", "1");
error_reporting(E_ALL);

$is_invalid = false;

if ($_SERVER["REQUEST_METHOD"] === "POST") {

    $mysqli = require __DIR__ . "/connection.php";

    $sql = sprintf("SELECT * FROM users
            WHERE user_name = '%s'",
            # prevent sql injection(below)
            $mysqli->real_escape_string($_POST["Username"]));

    $result = $mysqli->query($sql);

    $user = $result->fetch_assoc();

    if ($user) {

       if (password_verify($_POST["Password"], $user["password_hash"])) {

        session_start();

        session_regenerate_id();

        $_SESSION["id"] = $user["user_id"];
        echo "Successful Login :) ... redirecting";
        exit;
       }
    }

    $is_invalid = true;
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
    <title>Login to your account</title>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link href="https://fonts.googleapis.com/css?family=Roboto|Courgette|Pacifico:400,700" rel="stylesheet">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
    <link rel="stylesheet" type="text/css" href="css/signin.css">
</head>
<body>
<div class="signin-form">
    <form action="" method="post">
        <div class="form-header">
            <h2>Sign In</h2>
            <p>Login to MyChat</p>
        </div>
        <div class="form-group">
            <label>Email</label>
            <input type="text" class="form-control" name="Username" autocomplete="off" required="required">
        </div>
        <div class="form-group">
            <label>Password</label>
            <input type="password" class="form-control" placeholder="Password" name="Password" autocomplete="off" required="required">
        </div>
        <div class="small">Forgot password? <a href="forgot_pass.php">Click Here</a></div><br>
        <div class="form-group">
            <button type="submit" class="btn btn-primary btn-block btn-lg" name="sign_in">Sign in</button>
        </div>
        <?php #include("signin_user.php"); ?>   
    </form>
    <div class="text-center small" style='color:#67428B;'>Don't have an account? <a href="signup.php">Create one</a></div>
</div>
</body>
</html>    
connection.php
<?php
$con = mysqli_connect("localhost","root","","ecom") or die("Connection was not established");
?>
signup_user.php
<?php
ini_set("display_errors", "1");
ini_set("display_startup_errors", "1");
error_reporting(E_ALL);


#include("/connection.php");
include("/Applications/XAMPP/xamppfiles/htdocs/Ecom/chat/code/connection.php");


    if(isset($_POST['sign_up'])){
        
    # password hash:

    $password = $_POST['user_pass'];
    $confirm_password = $_POST['confirm_user_pass'];
    $pin = $_POST['user_pin'];
    $confirm_pin = $_POST['confirm_user_pin'];
    
    $password_hash = password_hash($password, PASSWORD_DEFAULT);
    $confirm_password_hash = password_hash($confirm_password, PASSWORD_DEFAULT);
    $pin_hash = password_hash($pin, PASSWORD_DEFAULT);
    $confirm_pin_hash = password_hash($confirm_pin, PASSWORD_DEFAULT);
    
    # pass hash data & POST data to db:

    $name = htmlentities(mysqli_real_escape_string($con,$_POST['user_name']));
    $pass = htmlentities(mysqli_real_escape_string($con,$password_hash));
    $confirm_pass = htmlentities(mysqli_real_escape_string($con,$confirm_password_hash));
    $pin = htmlentities(mysqli_real_escape_string($con,$pin_hash));
    $confirm_pin = htmlentities(mysqli_real_escape_string($con,$confirm_pin_hash));
    $rand = rand(1, 3); //Random number between 1 and 3

    # Register Validation
    if(empty($name)){
        echo "<script>alert('Username is required')</script>";
    }
    if(strlen($name) < 3) {
        echo "<script>alert('Username must be 3 - 30 characters')</script>";
        exit();
    }elseif(strlen($name) > 30) {
        echo "<script>alert('Username must be 3 - 30 characters')</script>";
        exit();
    }
    if(strlen($_POST['user_pass'])<12){
        echo "<script>alert('Password must be at least 12 characters')</script>";
        exit();
    }
    if(! preg_match("/[A-Z]/i", $_POST["user_pass"])){
        echo "<script>alert('Password must contain at least one capital letter')</script>";
        exit();
    }
    if (! preg_match("/[0-9]/", $_POST["user_pass"])) {
        echo "<script>alert('Password must contain at least one number')</script>";
        exit();
    }
    if (! preg_match("/[^a-zA-Z0-9]/", $_POST["user_pass"])) {
        echo "<script>alert('Password must contain at least one symbol')</script>";
        exit();
    }
    if ($_POST["user_pass"] !== $_POST["confirm_user_pass"]) {
        echo "<script>alert('Password must match')</script>";
        exit();
    }
    if (! is_numeric($_POST["user_pin"])) {
        echo "<script>alert('Pin must contain numbers only')</script>";
        exit();
    }
    if ($_POST["user_pin"] !== $_POST["confirm_user_pin"]) {
        echo "<script>alert('Pin must match')</script>";
        exit();
    }

    # Check for duplicate Username
    $check_username = "select * from users where user_name='$name'";
    $run_username = mysqli_query($con,$check_username);

    $check = mysqli_num_rows($run_username);

    if($check==1){

    echo "<script>alert('Username already exist, please try another!')</script>";
    echo "<script>window.open('signup.php','_self')</script>";
    exit();
    }
    }   

    # Pass php variable into sql db
    $insert = "insert into users (user_name,
                                user_pass,
                                confirm_user_pass,
                                user_pin,
                                confirm_user_pin)
                values ('$name',
                        '$pass',
                        '$confirm_pass',
                        '$pin',
                        '$confirm_pin')";

    $query = mysqli_query($con,$insert);

    # Register confirmation
    if($query){
    echo "<script>alert('Congratulations $name, your account has been created successfully.')</script>";
    echo "<script>window.open('signin.php','_self')</script>";
    }
    else {
    echo "<script>alert('Registration failed, try again!')</script>";
    echo "<script>window.open('signup.php','_self')</script>";
    }
}
?>