Get lyrics for any song using XMPP and PHP right into your IM – Add [email protected]

XMPP is soon finding it’s way into real time applications other than just chat. I have combined JAXL (Jabber XMPP client library written in PHP) and the API from lyricsfly.com to build a real time chat bot which can assist you with lyrics for any song. You can start using it by simply adding [email protected] to your IM account (e.g. Gtalk, Jabber etc). In this blog post, I will explain …

WordPress style “Duplicate comment detection” using Memcached and PHP

If you have a knack of leaving comments on blogs, chances are you might have experienced a wordpress error page saying “Duplicate comment detected; it looks as though you’ve already said that!“, probably because you were not sure that your comment was saved last time and you tried to re-post your comment. In this blog post, I will put up some sample PHP code for Duplicate comment detection using Memcached …

How to use locks in PHP cron jobs to avoid cron overlaps

Cron jobs are hidden building blocks for most of the websites. They are generally used to process/aggregate data in the background. However as a website starts to grow and there is gigabytes of data to be processed by every cron job, chances are that our cron jobs might overlap and possibly corrupt our data. In this blog post, I will demonstrate how can we avoid such overlaps by using simple …

How to add content verification using hmac in PHP

Many times a requirement arises where we are supposed to expose an API for intended users, who can use these API endpoints to GET/POST data on our servers. But how do we verify that only the intended users are using these API’s and not any hacker or attacker. In this blog post, I will show you the most elegant way of adding content verification using hash_hmac (Hash-based Message Authentication Code) …

How to use locks for assuring atomic operation in Memcached?

Memcached provide atomic increment and decrement commands to manipulate integer (key,value) pairs. However special care should be taken to ensure application performance and possible race conditions while using memcached. In this blog post, I will first build a facebook style “like” application using atomic increment command of memcached. Also, I will discuss various technical difficulty one would face while ensuring atomicity in this application. Finally, I will demo how to …

PHP tokens and opcodes : 3 useful extensions for understanding the working of Zend Engine

“PHP tokens and opcodes” – When a PHP script is executed it goes through a number of processes, before the final result is displayed. These processes are namely: Lexing, Parsing, Compiling and Executing. In this blog post, I will walk you through all these processes with a sample example. In the end I will list some useful PHP extensions, which can be used to analyze results of every intermediate process. …

Writing a custom unix style tail in PHP using Libevent API on Mac OS X 10.5.x and other platforms

Libevent is a library which provides a mechanism to execute a callback function when a specific event occurs on a file descriptor or after a timeout has been reached. Many famous applications/frameworks/libraries like memcached are using libevent. In this blog post, I will demonstrate how to write a custom unix style tail script using Libevent API in PHP. Setting up the environment: Setting up libevent with PHP is a little …

Use crumbs to protect your Ajax calls from Cross-site request forgery (CSRF/XSRF)

Have your API calls ever being used directly by someone without your permission? If yes, read on to find out how can we protect our API’s from such spammers and hackers. Before we go ahead and see a possible solution for this, lets try to list out a few cases, when our API’s can be accessed without our permissions. Common cases of vulnerable API/Ajax calls Ajax calls having no user …

5 exciting (gaming) bots you can create using Jaxl (Jabber XMPP Library) in PHP

Jaxl is an open source XMPP client library written in PHP. The object oriented structure of JAXL allow developers to build various extensions using Jaxl library as their base. If used intelligently, JAXL client library is capable of doing more than just chat message transfers. Here are a few applications where developers have tried using JAXL for delivering more than just chat messages: “I used your library to develop a …

Building a Custom PHP Framework with a custom template caching engine using Output Control functions

In past 1 year or so, I had opportunities of using a lot of php frameworks including zend, symfony, cakephp, codeigniter. All frameworks have their pros and cons, however that is out of scope of this blog post. You may want to checkout this comparison list of php frameworks here. In this blog post I will build a custom PHP framework (MVC Architecture). Then go on to discuss in brief …