JavaScript Remote Scripting: An AJAX-based Random Code Generator in Action

As you saw when I explained the function for generating rating links, each <a> element was responsible for triggering a GET request, in order to fetch the “process_input.php” file and obtain the corresponding random code. Considering this situation, let’s have a look at the structure of this file, which contains a few lines of PHP code. Its source code is as follows:

function getRandomString($length=4){
    if(!is_int($length)||$length<1){
        trigger_error('Invalid length for random string');
        exit();
    }
    $chars="ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    $randstring='';
    $maxvalue=strlen($chars)-1;
    for($i=0;$i<$length;$i++){
        $randstring.=substr($chars,rand(0,$maxvalue),1);
    }
    return $randstring;
}
// start or resume session
session_start();
// store challenge value in session variable
$_SESSION['challenge']=getRandomString();
// send challenge value to client
echo $_SESSION['challenge'];

As you can see, I’ve defined a simple PHP function for generating four-digit random strings. After defining the pertinent function, I’ve stored this value in a “challenge” session variable, which will be utilized by the server to determine whether the user has entered the correct code when proceeding to rate an article.

Of course, the most interesting thing here is how the server sends back the random value to the client. By simply echoing this value, the random code can be obtained through the “responseText” property that belongs to the “XMLHttpRequest object, and displayed accordingly.

Having provided you with all the proper explanations of each function involved in the implementation of the code generating application, the next thing to be done is to show the full source code for each file that integrates the program. Therefore, join me in the next few lines to see how the complete program code looks.