example

testhook.php

/**
* Check for post format type, apply filter based on post format name for easy modification.
*
* @since 1.0
*/
function chimps_post_formats_content() { 
	$format = get_post_format(); 
	$root = get_template_directory_uri(); 
	
	$content = '<div class="post_container">
		<div <?php post_class() ?> id="post-<?php the_ID(); ?>">
			<div class ="format-icon"><img src="<?php echo $root ;?>/images/formats/<?php echo $format;?>.png" height="50px" width="50px" /></div><h2 class="posts_title"><a href="<?php the_permalink() ?>"><?php the_title(); ?></a></h2>
				<div class="entry">
					<?php the_content(); ?>
				</div>
		</div><!--end post_class-->		
	</div><!--end post_container-->';
	
	return $content;
	
	apply_filters( 'chimps_post_formats_'.$format.'content', $content );
	
	echo "test";
}