verify_password = false，即使密码正确

Question

当我尝试登录verify_password编写的语句始终为false时，我遇到了问题。

<?php
if (isset($_POST['submit_login'])){

require 'connectionknygos.php';

$username = $_POST ['vardas'];
$password = $_POST ['slap'];    

    if(empty($username)||empty($password)){
        header("Location: frontpage.php?error=emptyfields");
        exit(); 
    }
    else{
        $sql = "SELECT * FROM vartotojai WHERE username = ?;";
        $stmt = mysqli_stmt_init($conn);
        if(!mysqli_stmt_prepare($stmt, $sql)){
            header("Location: frontpage.php?error=sqlerror");
        exit();
        }
        else{
            mysqli_stmt_bind_param($stmt, 's', $username);
            mysqli_stmt_execute($stmt);
            $result = mysqli_stmt_get_result($stmt);
            if($row = mysqli_fetch_assoc($result)){
                $passwordCheck = password_verify($password, $row['password']);
                if($passwordCheck == false){
                    header("Location: frontpage.php?error=wrongpasswordtest");
                    exit();
                }
                if($passwordCheck == true){
                    session_start();
                    $_SESSION['id'] = $row['id'];
                    $_SESSION['username'] = $row['username'];

                    header("Location: frontpage.php?login=success");
                    exit();
                }
                else{
                    header("Location: frontpage.php?error=wrongpassword");
                    exit();
                }
            }
            else{
                header("Location: frontpage.php?error=nouser");
                exit();
            }
        }
    }

    }