Create a PHP Login Form

A user login and registration system is super helpful when we want to store information about the users of our website. This applies to everything from educational websites which might store course progress and marks to e-commerce websites which will store information about customers’ past purchases.

In this tutorial, I’ll teach you how to create your own PHP login and registration forms from scratch.

Creating the Login and Registration Forms

Our first step will be the creation of a login form and a registration form. The forms will actually be pretty simple. The registration form will only ask for a username, email, and password. The username and email will be unique for everyone who registers. If anyone tries to create two accounts using the same email address, we will show them an error message letting them know that the email is already in use.

Coding the Registration Form

Here is the HTML for creating the registration form. You have to put it in a file named register.php.

The form is very basic, but we do use HTML5 in order to do some very basic input validation. For instance, the use of type="email" will alert users when the email address that they entered is not in the proper format. Similarly, the use of the pattern attribute on the username will make sure that the username only consists of alphanumeric characters.

You can read the tutorial titled Form Input Validation Using Only HTML5 and Regex if you want to learn more about the topic. You can also take client-side form validation to the next level with jQuery by getting more power over the error messages that are shown and their placement and appearance. If you want to learn more about client-side validation, check out those posts.

Coding the Login Form

Here is the HTML for the login form. You can put it in a file named login.php.

Style the Forms With CSS

Here is some CSS that you can apply to these forms:

This contains some additional styling rules for error messages and headings. The HTML and CSS from this section can be used as the basis of your project when you create your own forms which might require different styling and input fields.

Creating the User Table and Connecting to the Database

The next step is the creation of a user table that will store all the information about the registered users. In our case, the table simply consists of four columns: an auto-incrementing id, a unique username, an email, and a password.

You can use the following SQL to create the table quickly.

Now, create a file called config.php and write the following code in it to connect to the database.

Change the database name to whatever the name of your database is. This file will be used to establish a connection to the database.

Code the User Registration

It is finally time to implement the registration functionality. The main function of this code is to check if the supplied email is already registered. If it is not, we enter the username, email and password into the database.

Place the following code at the top of registration.php.

The first step is to include config.php and start the session. This helps us store any information that we want to preserve across the pages.

Next, we check if the user has clicked on the Register button to submit the form by checking if $_POST['register']has been set. Always remember that it is not a good idea to store passwords as plain text. For this reason, we use the password_hash() function and then store that hash in our database. This particular function creates a 60-character hash using a randomly generated salt.

Finally, we execute the query and check if a non-zero row number exists for a given email address. If it does, the user will get a message saying the email address is already registered.

If no row exists with the given email address, we enter the supplied information into our database and let the users know that the registration was successful.

Implementing the Login Functionality

In our last step, we wrote the code for logging users in. This time, we simply check the information in the database to see if the username and password combination entered into the form is correct.

Here is the code that goes at the top of login.php.

One important thing to note here is that we don’t compare the usernames and password in a single step. Because the password is actually stored in a hashed form, we first need to fetch the hash with the help of the supplied username. Once we have the hash, we can use the password_verify() function to compare the password and the hash.

Once we’ve successfully confirmed the password, we set the $_SESSION['user_id'] variable to the ID of that user in the database. You can also set the value of other variables here.

Restricting Access to Pages

Most websites where users are asked to register have some other pages where users access and store private data. You can use session variables to protect these pages. If the session variable is not set, simply redirect the users to the login page. Otherwise, show them the contents of the page.

The only thing that you have to do is to ensure the script contains session_start() at the beginning.

Resolving Common Errors

There are three types of errors that you might encounter when using this script:

1. Errors Due to Wrong Variable Names

One of the most common sources of error is having the wrong capitalization for a variable somewhere. Therefore, it is important to stick with the same naming convention for all your variables. As an example, consider the keys in the $_POST superglobal are based on the value of name assigned to input elements in the form. This means that $_POST['USERNAME'] and $_POST['username'] will have different values.

2. The ” Headers already sent” Error

Some functions like session_start() and header() modify HTTP headers. Since PHP flushes all headers before it outputs something, it is important to call all such functions before you output anything. This includes any raw HTML or unintentional spaces before the opening <?php tag.

3. Session Variables not Persisting Across Pages

You can access session variables on a page only if you called the function session_start() on that page. If you cannot access the values in $_SESSION superglobal on a page, this is probably because you forgot to call session_start(). Also remember to call the function before you output anything on the page. Otherwise, you will encounter the ” Headers already sent” error.

Final Thoughts

In this tutorial, we learned how to create a basic user registration and login system using PHP. Once you’ve grasped the basics of login and registration systems, you can create more complicated logic, for example allowing users to reset their password, or verify their email address.

You can also add more front-end validation with HTML5 attributes or jQuery to make the form more user-friendly.

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