I dont know how can i do this [closed]

I need help, I want to make it so that after clicking on the link, a message appears that it is leaving the website and it is related to danger and whether you really want to do it. I completely don't know how to do it in java or php and css?

<a href="<?php echo Tools::link($offer->contact_data()->www) ?>" target="_blank"><?php echo URL::idna_decode($offer->contact_data()->www) ?></a>

I need help, I want to make it so that after clicking on the link, a message appears that it is leaving the website and it is related to danger and whether you really want to do it. I completely don't know how to do it in java or php and css?

source https://stackoverflow.com/questions/76526181/i-dont-know-how-can-i-do-this