password_verify() function always returns false despite verifying repeatedly that common mistakes are mitigated

Question

I am trying to use password_verify in a project and despite using this function before without any issues, it is no longer working for me. I feel like I am overlooking something really small. Following is some of my code:

case 'Register':
    $first_name = trim(filter_input(INPUT_POST, 'first_name', FILTER_SANITIZE_FULL_SPECIAL_CHARS));
    $middle_name = trim(filter_input(INPUT_POST, 'middle_name', FILTER_SANITIZE_FULL_SPECIAL_CHARS));
    $last_name = trim(filter_input(INPUT_POST, 'last_name', FILTER_SANITIZE_FULL_SPECIAL_CHARS));
    $email = trim(filter_input(INPUT_POST, 'email', FILTER_SANITIZE_EMAIL));
    $password = trim(filter_input(INPUT_POST, 'password', FILTER_SANITIZE_FULL_SPECIAL_CHARS));
    $phone = trim(filter_input(INPUT_POST, 'phone', FILTER_SANITIZE_FULL_SPECIAL_CHARS));

    $email = checkEmail($email);
    $password = checkPassword($password);

    if (checkExistingEmail($email)){
        $_SESSION['message'] = '<p class="formErrorMessage">That email address is already in use. Try logging in or using a different email.</p>';
        include '../view/register.php';
        exit;
    }

    if (!empty($phone)){
        if (checkExistingPhone($phone)){
            $_SESSION['message'] = '<p class="formErrorMessage">That phone number is already in use. Please use a different phone number.</p>';
            include '../view/register.php';
            exit;
        }
    }

    if (empty($first_name) || empty($last_name) || empty($email) || empty($password)){
        $_SESSION['message'] = '<p class="formErrorMessage">Please provide information for all required form fields.</p>';
        include '../view/register.php';
        exit;
    }

    $hashedPassword = password_hash($password, PASSWORD_DEFAULT);

    $registrationOutcome = registerUser($first_name, $middle_name, $last_name, $email, $hashedPassword, $phone);

    if($registrationOutcome === 1){
        setcookie('first_name', $first_name, strtotime('+1 year'), '/');
        $userData = getUser($email);

        $_SESSION['loggedin'] = TRUE;

        array_pop($userData);

        $_SESSION['clientData'] = $clientData;

        header('Location: /valleymusicclub/accounts/');
        exit;
    } else {
        $_SESSION['message'] = "<p class='formErrorMessage'>Sorry, $first_name, but the registration failed. Please try again.</p>";
        include '../view/login.php';
        exit;
    }
    break;
case 'Login':
    $email = filter_input(INPUT_POST, 'email', FILTER_SANITIZE_EMAIL);
    $email = checkEmail($email);
    $password = filter_input(INPUT_POST, 'password', FILTER_SANITIZE_FULL_SPECIAL_CHARS);
    $passwordCheck = checkPassword($password);

    if (empty($email) || empty($passwordCheck)){
        $_SESSION['message'] = '<p class="formErrorMessage">Please provide a valid email address and password.</p>';
        include '../view/login.php';
        exit;
    }

    $userData = getUser($email);

    $passwordHash = $userData['password'];

    $hashCheck = password_verify($password, $passwordHash);

    if (!$hashCheck){
        $_SESSION['message'] = "<p class='formErrorMessage'>Please provide a valid password. $password</p>";
        include '../view/login.php';
        exit;
    }

    $_SESSION['loggedin'] = TRUE;

    array_pop($clientData);

    $_SESSION['clientData'] = $clientData;

    header('Location: /valleymusicclub/accounts/');
    exit;

The thing that is baffling me is that this is almost the exact same code structure as another project I did a while back and used as a base, which prior project is STILL working on the same machine. After doing a var_dump on the function, I verified that it always returns false, even after ensuring multiple times that I am using the same password as originally put in the database.

I did some research looking into the common pitfalls for this issue. I verified that my database is a VARCHAR with 255 limit to account for the minimum 60 characters for default hash. I checked that the password was hashing once going into the database, which it is. I verified that the $userData['password'] variable holds the hashed password, which it does. I verified that the password I am passing through to the $password variable through the form is indeed the password that I typed in, which it is. I also made sure that I am not passing a hashed password in the first parameter of the function and that I am passing a hashed password as the second parameter. I am honestly at a loss. It just doesn't make sense that the same code works in a different project and not this one, even after quadruple checking everything that could go wrong.

Edit: I understand that filters can affect these things, but as I said before, this code is taken straight from a project that is working as intended, even with filters. Following is code that is working currently:

case 'register':
    $clientFirstname = trim(filter_input(INPUT_POST, 'clientFirstname', FILTER_SANITIZE_FULL_SPECIAL_CHARS));
    $clientLastname = trim(filter_input(INPUT_POST, 'clientLastname', FILTER_SANITIZE_FULL_SPECIAL_CHARS));
    $clientEmail = trim(filter_input(INPUT_POST, 'clientEmail', FILTER_SANITIZE_EMAIL));
    $clientPassword = trim(filter_input(INPUT_POST, 'clientPassword', FILTER_SANITIZE_FULL_SPECIAL_CHARS));

    $clientEmail = checkEmail($clientEmail);
    $checkPassword = checkPassword($clientPassword);

    $existingEmail = checkExistingEmail($clientEmail);

    // Check for existing email address in the table
    if($existingEmail){
        $message = '<p class="formErrorMessage">That email address already exists. Do you want to login instead?</p>';
        include '../view/login.php';
        exit;
    }

    // Check for missing data
    if(empty($clientFirstname) || empty($clientLastname) || empty($clientEmail) || empty($checkPassword)){
        $message = '<p class="formErrorMessage">Please provide information for all empty form fields.</p>';
        include '../view/registration.php';
        exit;
    }

    // Hash the checked password
    $hashedPassword = password_hash($clientPassword, PASSWORD_DEFAULT);

    // Send the data to the model
    $regOutcome = regClient($clientFirstname, $clientLastname, $clientEmail, $hashedPassword);

    // Check and report the result
    if($regOutcome === 1){
        setcookie('firstname', $clientFirstname, strtotime('+1 year'), '/');
        $_SESSION['message'] = "<p class='formSuccessMessage'>Thanks for registering, $clientFirstname. Please use your email and password to login.</p>";
        header('Location: /phpmotors/accounts/?action=login');
        exit;
    } else {
        $_SESSION['message'] = "<p class='formErrorMessage'>Sorry, $clientFirstname, but the registration failed. Please try again.</p>";
        include '../view/login.php';
        exit;
    }
    break;
case 'Login':
    $clientEmail = filter_input(INPUT_POST, 'clientEmail', FILTER_SANITIZE_EMAIL);
    $clientEmail = checkEmail($clientEmail);
    $clientPassword = filter_input(INPUT_POST, 'clientPassword', FILTER_SANITIZE_FULL_SPECIAL_CHARS);
    $passwordCheck = checkPassword($clientPassword);

    // Run basic checks, return if errors
    if (empty($clientEmail) || empty($passwordCheck)) {
        $_SESSION['message'] = '<p class="formErrorMessage">Please provide a valid email address and password.</p>';
        include '../view/login.php';
        exit;
    }
    
    // A valid password exists, proceed with the login process
    // Query the client data based on the email address
    $clientData = getClient($clientEmail);
    // Compare the password just submitted against
    // the hashed password for the matching client
    $hashCheck = password_verify($clientPassword, $clientData['clientPassword']);
    // If the hashes don't match create an error
    // and return to the login view
    if(!$hashCheck) {
        $_SESSION['message'] = '<p class="formErrorMessage">Please check your password and try again.</p>';
        include '../view/login.php';
        exit;
    }
    // A valid user exists, log them in
    $_SESSION['loggedin'] = TRUE;
    // Remove the password from the array
    // the array_pop function removes the last
    // element from an array
    array_pop($clientData);
    // Store the array into the session
    $_SESSION['clientData'] = $clientData;
    // Send them to the admin view
    header('Location: /phpmotors/accounts/');
    exit;

I also tried removing the filters, trim, etc., and it still is not working. Yes, I verified that the trimmed/filtered password is producing a string that matches my original password. I would agree that using filters before verifying that it works in the first place is the right way to go, but I have used this structure as demonstrated here and it works just fine in the prior project. I don't understand what is different between them.

Edit 2: I just added code to each of my projects to compare their outputs. Here is the code I added to the project that is working:

    $clientData = getClient($clientEmail);

    // var dumps for troubleshooting purposes
    var_dump($clientPassword);
    var_dump($clientData['clientPassword']);

    // Compare the password just submitted against
    // the hashed password for the matching client
    $hashCheck = password_verify($clientPassword, $clientData['clientPassword']);

    var_dump($hashCheck);

Following is the output: string(12) "Password123@" string(60) "$2y$10$gPmIdgHMtKEa28EagP4H3.TDZrWwoMY/CABIQleOqXUzh65/fov6W" bool(true)

Here is the code I added to the project currently having trouble:

    $userData = getUser($email);

    $passwordHash = $userData['password'];

    var_dump($password);
    var_dump($passwordHash);

    $hashCheck = password_verify($password, $passwordHash);

    var_dump($hashCheck);

This is the output: string(12) "Password123@" string(60) "$2y$10$8wheUb4qjxl.V1qM5EsKf.nE.MEF5wE8rnfnDApIMRjpIFxhgVt/2" bool(false)

Just a quick note: all I added were var_dumps. I did not change anything else about the code.