Joomla 2.5

Hello everyone. As you may or may not know, the official Joomla 2.5 has been out for a while now and I intend to create some new tutorials regarding it. So stay tuned...

Check the group id of a user in Joomla

If you are doing your own custom Joomla component, somtimes it is very helpful to determine the user group of a user in order to perform necessary actions (for example, only admins can delete a record).

For doing this, we must get the group id. They are as follows:

Public : 0
Registered : 1
Special : 2

Users that have access to the backend fall under the Special group.

The following code will check the group id of the current user and display a message if user is not of 'Special' type.

$user = JFactory::getUser();
$userGID = $user->get('gid');
if ($userGID != 2)
{
   echo "You do not have the necessary permissions to perform this action.";
}

Using 'NOT IN' in MySQL

Suppose we have a table called USERS that has a primary key 'id' and another table SUBSCRIPTIONS with foreign key 'uid'.

If we want to remove all subscriptions (from the SUBSCRIPTIONS table) that does not correspond to any user, we can run this MySQL query:

DELETE FROM SUBSCRIPTIONS WHERE uid NOT IN (SELECT id from USERS)

What we are doing here is getting a list of all the ids from the USERS table and then deleting all rows from the SUBSCRIPTIONS table where the user id (uid) does not correspond to any id in the USERS table. Very simple.

Note: Throughout this blog, you will find many books that are for sale on Amazon. I recommend you get these books while learning web programming as they will help strengthening your skills.

How to dynamycally remove an external Javascript or CSS file from a page

The key is to doing this is to traverse the DOM and then call the DOM's deleteChild() method.

We can identify the file to be deleted by using its filename or CSS class name. Here I am going to use its filename.

function deletejscssfile(filename, filetype){

var targetelement=(filetype=="js")? "script" : (filetype=="css")? "link" : "none" //determine element type to create nodelist from

var targetattr=(filetype=="js")? "src" : (filetype=="css")? "href" : "none" //determine corresponding attribute to test for

var allsuspects=document.getElementsByTagName(targetelement)

for (var i=allsuspects.length; i>=0; i--){ //search backwards within nodelist for matching elements to delete

if (allsuspects[i] && allsuspects[i].getAttribute(targetattr)!=null && allsuspects[i].getAttribute(targetattr).indexOf(filename)!=-1)

allsuspects[i].parentNode.deleteChild(allsuspects[i]) //delete element by calling parentNode.deleteChild()

}

}

deletejscssfile("script_to_be_removed.js", "js") //delete all occurences of “script_to_be_removed.js” on page

deletejscssfile("script_to_be_removed.css", "css") //delete all occurences of “script_to_be_removed.css” on page

Recommended Joomla books

I have come across these books during my career as a programmer and I can say, they are worth every penny. I highly recommend you buy them if you are into Joomla development.


Joomla! Start to Finish: How to Plan, Execute, and Maintain Your Web Site
$38.54











Joomla! 1.5: A User's Guide: Building a Successful Joomla! Powered website
$29.69










Joomla! Bible
$29.69








Learning Joomla! 1.5 Extension Development
$34.08