alert.php

<?php
function alertMessage($type, $messsage)
{
    if ($type == 0) {
        echo "<div class=\"alert\">";
    } else if ($type == 1) {
        echo "<div class=\"alert info\">";
    }
    echo "<span class=\"closebtn\" onclick=\"this.parentElement.style.display='none';\">
          <i class=\"fas fa-times\"></i>
          </span>" . $messsage . "</div>";
}
if (isset($_GET['error'])) {
    if ($_GET['error'] === 'param-missing') {
        alertMessage(0, 'Please complete all fields.');
    } elseif ($_GET['error'] === 'paramsnotvalid') {
        alertMessage(0, 'E-mail and username are not valid.');
    } elseif ($_GET['error'] === 'email-not-valid') {
        alertMessage(0, 'E-mail address is not valid.');
    } elseif ($_GET['error'] === 'username-not-valid') {
        alertMessage(0, 'Username is not valid (only alphabetical and numerical characters are allowed).');
    } elseif ($_GET['error'] === 'pwddiff') {
        alertMessage(0, 'Password entered did not match with repeated password.');
    } elseif ($_GET['error'] === 'usernotexist') {
        alertMessage(0, 'User does not exist on our system.');
    } elseif ($_GET['error'] === 'amount-invalid') {
        alertMessage(0, 'Please enter the correct amount.');
    } elseif ($_GET['error'] === 'name-invalid') {
        alertMessage(0, 'The name wasn\'t valid (only alpha numerical and spaces are allowed).');
    } elseif ($_GET['error'] === 'permdenied') {
        alertMessage(0, 'Please sign in to view the page.');
    } elseif ($_GET['error'] == 'usernameexsit'){
        alertMessage(0, 'Username already exist try again');
    }
} elseif (isset($_GET['signup']) && $_GET['signup'] === 'success') {
    alertMessage(1, 'Sign up successful. You can sign in now.');
} elseif (isset($_GET['signin'])) {
    if ($_GET['signin'] === 'failed') {
        alertMessage(0, 'Authentication failed, please try again.');
    } elseif ($_GET['signin'] === 'success') {
        alertMessage(1, 'Sign in successful.');
    }
} elseif (isset($_GET['pwdchange'])) {
    if ($_GET['pwdchange'] === 'success') {
        alertMessage(1, 'The password has been changed, You can now sign in with the new password.');
    } elseif ($_GET['pwdchange'] === 'failed') {
        alertMessage(0, 'Password change faild, please try again');
    }
} elseif (isset($_GET['email']) && $_GET['email'] === 'sent') {
    alertMessage(1, 'Email has been sent, please check your mail box for instructions.');
} elseif (isset($_GET['changeinfo']) && $_GET['changeinfo'] === 'success') {
    alertMessage(1, 'Your account information has been changed.');
} elseif (isset($_GET['deletebill']) && $_GET['deletebill'] === 'success') {
    alertMessage(1, 'The bill has been deleted');
} elseif (isset($_GET['confirmbill']) && $_GET['confirmbill'] === 'success') {
    alertMessage(1, 'The bill has been confirmed');
}