UPDATE: Okay, Looking at the Error, it should be easy. Just remove any Whitespaces or Clear Lines at the end of your Plugin file after the last “?>”.
http://php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc
Did you copy&paste the code here? Because it seems like you have some whitespaces that should not be there in the line
<?php if ($the_query->have_posts()) : while ($the_query->have_posts()) : $the_query- >the_post(); ?>
If you remove the whitespaces (like this:
<?php if ($the_query->have_posts()) : while ($the_query->have_posts()) : $the_query->the_post(); ?>
), it should work.
P.S.: Don’t forget to use
<?php wp_reset_postdata(); ?>
after the
<?php endwhile; ?>
Otherwise it could end up messing with the rest of your page ^^
Happy Coding,
Kuchenundkakao