I want to be able to indicate in a field where one can enter a username immediately after leaving the field whether the chosen username already exists or not yet.

I have already found the code below for this.

$database = JFactory::getDBO();
$user = ''; //This is where the value of the username field should be
$database->setQuery("SELECT username FROM #__users WHERE username='".$user."'");
$database->query();
if (intval($database->loadResult()) >= 1)
{
echo 'Your chosen username already exists on this website';
}

But how do I get this code to run after exiting the field.
And a message is given whether the chosen username already exists or not yet.

Hello,

What you are describing requires an AJAX custom script that will be triggered when the focus is moved to a different field. The script should check for the username availability using a code similar to the one you have provided and return a message informing the submitting user if the username is available or not.

andreic wrote:
Okay
But how can I make this?
Or is it also possible as a validation.

I have searched a lot but couldn't find anything.

A validation is also an option.

Can you help me.