PHP command problem

Hi, I use Local by Flywheel a lot and I really like it, it’s great to manage my WP sites.
However I had a problem lately, some pages of some websites were impossible to dispay through the “Live Link” feature, but these pages had no problem on local browsers.
I finally find out that a PHP line was the problem :
<?php list($width, $height) = getimagesize($im); ?>
If I delete this line from the page everything works fine, so if it can help to fix the problem, it would be great !