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Thursday, April 24, 2008

An Example of User Authentication System in PHP

In this post we’re going to create a very simple user authentication system in PHP. It’d be like the one’s you see while logging in to various sites/services (emails, forums, social networking sites etc)

User authentication is a way for sites to know who you are among the other registered users and showing you relevant content (may be confidential). For example it’s only you ho is authorized to see your emails because you only know your authentication information.

In this post we’re going to create two files, a HTML page which will collect the username and password in a form. These information will then be send to a PHP script, which will verify and show the required information.

Below is the PHP code:


  <?php
  //define some constants
  define("USERNAME",  "goodjoe");
  define("PASSWORD",  "123456");
  define("REALNAME",  "Joe Burns");

  //have the data being passed
  $user=$_GET['user'];
  $pass=$_GET['pass'];

  //if username and password match
  if($user==USERNAME && $pass==PASSWORD)
  {
    echo "<h1>Hello ".REALNAME."</h1>";
    echo "<p>Nice to see you logging in again...</p>";
    echo "<p>USER: <i>".USERNAME."</i></p>";
  }
  //if not
  else
  {
    echo "<h1>Wrong username or password!</h1>";
  }
  ?>

The code above is pretty straightforward. You may change the constants that hold the user information.

Now, as you know from Taking User Inputs to Create Personalized Pages II, we need a HTML page with a form to send information to this script. Here it is:


  <html>
  <head>
  <title>Simple Uesr Authentication System</title>
  </head>

  <body>
  <form name="form1" method="get" action="verify.php">
    <p>Uername
      <input name="user" type="text" id="user">
    </p>
    <p>Password
      <input name="pass" type="password" id="pass">
    </p>
    <p>
      <input type="submit" name="Submit" value="Submit">
    </p>
  </form>
  </body>
  </html>

Refer to Taking User Inputs to Create Personalized Pages II to know more about the form tag. Note that the PHP script must be of the name as in the “action=…” of the form tag and in the same directory as the HTML page.

Notice this line

   <input name="pass"    type="password" id="pass">

The above code creates an element that shows asterisks (*) on entering anything, just like on other sites.

Now, we’re ready to put these files on the server and request the HTML page. Do it and play with the page for a while!

Creating a Simple User Authentication System in PHP

This is how it’d look.

A few points to note:

  • This is a very simple example and holds the user information in the script itself (hard coded). Real sites store user information in Databases.

  • For real-life applications, we’d also need to use session variables or cookies.

[Update: Read the next post An Example of User Authentication System in PHP II]

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