Developing a Login System with PHP and MySQL

Introduction

Most interactive websites nowadays would require a user to log in into the website’s system in order to provide a customized experience for the user. Once the user has logged in, the website will be able to provide a presentation that is tailored to the user’s preferences. 

Main

A basic login system typically contains 3 components:
1. The component that allows a user to register his preferred login id and password.
2. The component that allows the system to verify and authenticate the user when he subsequently logs in.
3. The component that sends the user’s password to his registered email address if the user forgets his password.

Such a system can be easily created using PHP and MySQL.

Component 1 – Registration

Component 1 is typically implemented using a simple HTML form that contains 3 fields and 2 buttons:
1. A preferred login id field
2. A preferred password field
3. A valid email address field
4. A Submit button
5. A Reset button

Assume that such a form is coded into a file named register.html. The following HTML code excerpt is a typical example. When the user has filled in all the fields, the register.php page is called when the user clicks on the Submit button. 

[ form name="register" method="post" action="register.php"]
[ input name="login id" type="text" value="loginid" size="20"/][br]
[ input name="password" type="text" value="password" size="20"/][br]
[ input name="email" type="text" value="email" size="50"/][br]
[ input type="submit" name="submit" value="submit"/]
[ input type="reset" name="reset" value="reset"/]
[ /form]

The following code excerpt can be used as part of register.php to process the registration. It connects to the MySQL database and inserts a line of data into the table used to store the registration information.

[@mysql_connect("localhost", "mysql_login", "mysql_pwd") <BR>or die("Cannot connect to DB!");
@mysql_select_db("tbl_login") <BR>or die("Cannot select DB!");
$sql="INSERT INTO login_tbl (loginid, password and email) VALUES (".$loginid.???,???.$password.???,???.$email.???)???;
$r = mysql_query($sql);
if(!$r) <BR>{
$err=mysql_error();
print $err;
exit();
}

The code excerpt assumes that the MySQL table that is used to store the registration data is named tbl_login and contains 3 fields – the loginid, password and email fields. The values of the $loginid, $password and $email variables are passed in from the form in register.html using the post method.

Component 2 – Verification and Authentication

A registered user will want to log into the system to access the functionality provided by the website. The user will have to provide his login id and password for the system to verify and authenticate. This is typically done through a simple HTML form. This HTML form typically contains 2 fields and 2 buttons:
 
1. A login id field
2. A password field
3. A Submit button
4. A Reset button

Assume that such a form is coded into a file named authenticate.html. The following HTML code excerpt is a typical example. When the user has filled in all the fields, the authenticate.php page is called when the user clicks on the Submit button.

[form name="authenticate" method="post" action="authenticate.php"]
[input name="login id" type="text" value="loginid" size="20"/][br]
[input name="password" type="text" value="password" size="20"/][br]
[input type="submit" name="submit" value="submit"/]
[input type="reset" name="reset" value="reset"/]
[/form]

The following code excerpt can be used as part of authenticate.php to process the login request. It connects to the MySQL database and queries the table used to store the registration information.

@mysql_connect("localhost", "mysql_login", "mysql_pwd") <BR>or die("Cannot connect to DB!");
@mysql_select_db("tbl_login") <BR>or die("Cannot select DB!");
$sql="SELECT loginid FROM login_tbl WHERE loginid=’".$loginid.???’ and password=’???.$password.???’???;
$r = mysql_query($sql);
if(!$r) <BR>{
$err=mysql_error();
print $err;
exit();
}
if(mysql_affected_rows()==0){
print "no such login in the system. please try again.";
exit();
}
else{
print "successfully logged into system.";
//proceed to perform website’s functionality – e.g. present information to the user
}

 
[form name="forgot" method="post" action="forgot.php"]
[input name="login id" type="text" value="loginid" size="20"/][br]
[input type="submit" name="submit" value="submit"/]
[input type="reset" name="reset" value="reset"/]
[/form]

@mysql_connect("localhost", "mysql_login", "mysql_pwd") <BR>or die("Cannot connect to DB!");
@mysql_select_db("tbl_login") <BR>or die("Cannot select DB!");
$sql="SELECT password, email FROM login_tbl WHERE loginid=’".$loginid.???’???;
$r = mysql_query($sql);
if(!$r) <BR>{
$err=mysql_error();
print $err;
exit();
}
if(mysql_affected_rows()==0)<BR>{
print "no such login in the system. please try again.";
exit();
}
else <BR>{
$row=mysql_fetch_array($r);
$password=$row["password"];
$email=$row["email"];
$subject="your password";
$header="from:you@yourdomain.com";
$content="your password is ".$password;
mail($email, $subject, $row, $header);
print "An email containing the password has been sent to you";
}
 

Conclusion

The above example is to illustrate how a very basic login system can be implemented. The example can be enhanced to include password encryption and additional functionality – e.g. to allow users to edit their login information. - Used with the author’s permission. 

References

This article is taken from http://www.chauy.com/2005/12/developing-a-login-system-with-php-and-mysql