Issue

I have a wordpress function that displays adverts every so often. When are not shown essentially I would prefer to the div to display:none;

I can not seem to figure out the correct PHP function in order for the div not to display when a advert is uploaded.

<div class="advert" <?php if(!empty($_GET['details'])) {echo "style='display: none'";} ?>></div>

Solution

Why not completely not echo "advert" element?

   if ( !empty($_GET['details']) ){
       echo '<div class="advert">add text</div>';
    }

if you really want to just hide, you can assign hide class

<div class="advert <?php echo ( empty($_GET['details'])? 'hide' : '' );">add text</div>

then you would need to add "hide" class with display:none in your style.css

Above is shorthand/ternary if/else statement used, its great if you need output some string.

And, please don't output/trust any user input i.e. $_GET['details'] 'as is' anywhere without escaping it, for security reasons.

Wordpress have plenty easy-to-use escape functions, like esc_attr() and esc_html().

Answered By - Maximus Light