Publishers of technology books, eBooks, and videos for creative people

Home > Articles > Web Design & Development > PHP/MySQL/Scripting

This chapter is from the book

Logging In

Logging in to the site is a two-step process: completing the form and validating the submitted values against the database. The login form is not its own page—it’s shown in the sidebar to all non-logged-in users. For this reason, the login form can’t use the same single-script approach as in register.php. The question then becomes: where should the user end up when he successfully logs in and when he doesn’t? In both cases, I decided the user should end up back on the home page; for this reason, the login form gets submitted to index.php. Hence, the index page needs to be updated with the code for handling the form. Rather than writing that code directly into the home page, it’s better to include it as a separate file, just after the database connection but prior to the inclusion of the header file:

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
   include('./includes/login.inc.php');
}

This is feasible because normally index.php will be requested via GET. If it’s a POST request, the login form has been submitted, and this script includes the file that will test the login credentials.

Processing the Form

I think it will be easier to follow the login process if I talk about the form last, so let’s first look at the code that handles the login form. That process needs to do the following in this order:

  1. Validate the submitted email address and password.
  2. Compare the submitted values with those in the database.
  3. Define errors if the values are incorrect.
  4. Store data in a session if the values are correct.

Here’s how all of that works in actual code:

  1. Create a new PHP script in your text editor or IDE to be named login.inc.php.

    This will be stored in the includes directory.

  2. Create an empty array for recording errors:

    <?php
    $login_errors = array();

    This errors array will be used just like $reg_errors in the registration script.

  3. Validate the email address:

    if (filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
       $e = escape_data($_POST['email'], $dbc);
    } else {
       $login_errors['email'] = 'Please enter a valid email address!';
    }

    This code replicates that in the registration process, using PHP’s Filter extension to validate the email address.

  4. Validate the password:

    if (!empty($_POST['pass'])) {
       $p = $_POST['pass'];
    } else {
       $login_errors['pass'] = 'Please enter your password!';
    }

    To validate the password, I’m just making sure it’s not empty. Part of the reason is performance—this will be faster than the zero-width positive lookahead regular expression used in the registration process—and part of the reason will be explained later in the chapter.

    In theory, you don’t need to validate the submitted values because the database query will be confirming whether the submitted values are correct. However, database queries are expensive (in terms of server resources and performance), so it’s best not to run one unless necessary.

  5. If there are no errors, query the database:

    if (empty($login_errors)) {
       $q = "SELECT id, username, type, pass, IF(date_expires >= NOW(), true, false) AS expired FROM users WHERE email='$e'";
       $r = mysqli_query($dbc, $q);

    The basic query selects five values from the users table: the user’s ID, username, type, password, and account expiration. The WHERE clause checks that the email address matches the submitted email address. The password will be checked in the PHP code.

    For the account expiration, I’m doing something that may be new to you. I don’t care when the user’s account expires, only whether it’s valid right now. One way of accomplishing this would be to select the expiration value, which is a date, and then use PHP to convert it into a timestamp and compare it to the current timestamp. That’s a lot of code and logic to put onto PHP. Instead, I’m doing an IF conditional within my MySQL query. That syntax is just

    IF(date_expires >= NOW(), true, false)

    The first expression is the condition being tested; the second is what’s returned if the condition is true; the third value is what’s returned if the condition is false. Thus, if the expiration date is greater than or equal to this moment, the value true will be selected.

  6. If one row was returned by the database query, fetch the data:

    if (mysqli_num_rows($r) === 1) {
       $row = mysqli_fetch_array($r, MYSQLI_ASSOC);

    This conditional will be true if the email address exists in the database.

  7. Compare the password against the stored password:

    if (password_verify($p, $row['pass'])) {

    This code was explained at the beginning of the chapter, and it lets you verify a submitted password against a stored one. Again, you’ll need to include the password_compat library before this line if you’re using a version of PHP prior to 5.5.

  8. If the user is an administrator, create a new session ID, just to be safe:

    if ($row['type'] === 'admin') {
       session_regenerate_id(true);
       $_SESSION['user_admin'] = true;
    }

    If the user is an administrator, two things must be done. First, the session identifier ought to be changed as a security measure. Doing so prevents session fixation attacks (where a hacker sets a user’s session ID to match the hacker’s own session ID, then gets the administrator to log in, thereby giving the hacker administrative authority). The session_regenerate_id() function serves this purpose.

    Next, I only want to create a $_SESSION['user_admin'] element with a true value if the user’s type equals admin. Understand that I don’t want to create a $_SESSION['user_admin'] element equal to false if the user’s type is member. This is because the function that will validate a user’s access to pages—redirect_invalid_user() in config.inc.php—will check only if a session variable is set, not what its actual value is.

  9. Store the other data in the session:

    $_SESSION['user_id'] = $row['id'];
    $_SESSION['username'] = $row['username'];
    if ($row['expired'] === 1) $_SESSION['user_not_expired'] = true;

    First, the user’s ID and name are stored in the session, but given user<something> names so that they won’t possibly conflict later on with anything else I might store in the session.

    For the expiration, I only want to store a value indicating that the account hasn’t expired. MySQL will return the number 1 for the Boolean value true, so if $row['expired'] (which is the value in the array for the expiration status) equals that, I create a new element in $_SESSION. Again, I’m not assigning a value if the account has expired.

  10. If the password didn’t match, or if no database row was returned, create an error message:

       } else {
          $login_errors['login'] = 'The email address and password do not match those on file.';
       }
    } else {
       $login_errors['login'] = 'The email address and password do not match those on file.';
    }

    The same error message will be used if the user supplied a valid email address but the password didn’t match that stored in the database, or if the email address wasn’t found in the database at all. For security purposes, the script doesn’t indicate which of the two values is incorrect, or if the email address has been registered at all.

  11. Complete the script:

    } // End of $login_errors IF.

    As with all other scripts that will be included by other scripts, I’m omitting the closing PHP tag.

  12. Save the file.

Creating the Form

The next script to discuss, login_form.inc.php, is the first step in the process. It needs to do just two things: present a form and report any errors that occurred when the form was submitted. The form contains two inputs: one for the email address and one for the password. Both are created using the same create_form_input() function, which means that the form_functions.inc.php script must be included. The function needs to take an array of errors—$login_errors—as its fourth argument. That array is created in login.inc.php. However, if the user is just loading the login form for the first time, $login_errors won’t exist, so this script should initialize an empty array in that case.

Here’s the complete login_form.inc.php:

<?php
if (!isset($login_errors)) $login_errors = array();
require('./includes/form_functions.inc.php');
?>
<form action="index.php" method="post" accept-charset="utf-8">
<fieldset>
<legend>Login</legend>
<?php
if (array_key_exists('login', $login_errors)) {
   echo '<div class="alert alert-danger">' . $login_errors['login'] . '</div>';
}
create_form_input('email', 'email', '', $login_errors, array('placeholder'=>'Email address'));
create_form_input('pass', 'password', '', $login_errors, array('placeholder'=>'Password'));
?>
<button type="submit" class="btn btn-default">Login &rarr;</button>
</fieldset>
</form>

By default, all errors are reported via the create_form_input() function. However, this form is a bit different in that login.inc.php could create an error (that is, an element in the $login_errors array) not associated with a particular form input. That error results when both fields are properly filled out but the values don’t, together, match a record in the database. In that case, the $login_errors['login'] element is assigned an error message. Therefore, the form first checks if that array element exists in $login_errors, in which case the error message will be displayed just before the two inputs (Figure 4.8). Other error messages are associated with the offending form input (Figure 4.9).

Figure 4.8

Figure 4.8

Figure 4.9

Figure 4.9

Peachpit Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Peachpit and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Peachpit products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email ask@peachpit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by Adobe Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.peachpit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020