Upgrade the web

In this third part of the tutorial we are going to create an important part of the application. We will learn how to register a new user and save this user to the database, when a user is created it should of course be possible for him to log in. We will accomplish the login part by using session variables.

Well lets start with how to register a user. The first thing we will need is some text boxes with html to put in the desired username and password.

Join my community
Username:

Password:

This code creates two text boxes that is supposed to hold the username and password, when the form is submitted the contents of the text boxes is forwarded to the file signup.php.

connect();                               // Connect to the database
			$query = "SELECT * FROM members WHERE username='".$_POST["username"]."'";
			$result = $db->query($query);
			$result = mysql_num_rows($result);

			if($result!="0")
				echo "Username already exists!";
			else
			{
				// Create a query that inserts the data from the form to the database
				$query = "INSERT INTO members(username,password) VALUES('".$_POST["username"]."','".$_POST["password"]."')";

				$result = $db->query($query);
				echo "Signed up succesfully you can now log in";
			}
		}
		else
		{
			echo "Error: No username or password supplied, try again.";
		}

	}
	else
		echo "Error: please fill in the signup form";
}
?>

The first thing this file does is to check if we have valid data submitted from the html form we created above we do this using the php functions $_GET and $_POST. Get is used to get variables passed from file to file with php as from our example above (signup.php?submit) we set the variable submit as the forms submit button is pressed. Post is used to get data passed from a form in the example above we get the values of the text boxes where the username and password is written.

When we have made sure we have valid data in these variables we proceed and sets up a connection to the database and trues to select the username from the database. We do this to make sure we don get any duplicate entries. If the username does not exist we can proceed and insert the new data into the database.

The next step is to log in, as mentioned above we will use sessions for this task. First we create a html form like above but instead of calling signup.php we call login.php

connect();
	$query = "SELECT * FROM members WHERE username='$username' AND password='$password'";
	$result = $db->query($query);
	$result = mysql_num_rows($result);  // Does the row exists?

	if($result!="0"){
	// authenication correct lets login
	$_SESSION["password"] = $password;;
	$_SESSION["username"] = $username;
	header("Location: member.php?id=$username");
	}
	else
	{
		echo "Wrong username or password. Please try again!";
	}
}
?>

This code first checks to see if the username exists if it does it goes on to make sure the password is correct. If everything looks correct it registers two session variables with $_SESSION called username and password and forwards the user to our main page member.php.

Next part: Presentation