Plugin conflict: PHP code for posts and Advanced custom fields

When making custom loops to put into a page, I use the plugin PHP Code For Posts so that the PHP executes. However, I noticed that if I did so with the Advanced Custom Fields plugin active, the loop was rewritten as in this example:

<!--?php $thisQuery = new WP_Query('cat=34&posts_per_page=3');<br ?--> while ($thisQuery->have_posts() ) :
$thisQuery->the_post();
the_title();
the_content();
get_the_post_thumbnail();
endwhile;
?>

Of course, the page then just displays the PHP code, or what looks like it, but it does not run.

I’d be interested in hearing of any workarounds or explanations. (This is not an actual problem for me as yet; I was able to deactivate the ACF plugin and just not use it.)

Thanks! Hope this helps someone with a similar problem.