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At times, I need to return the output of a loop (usually with WP_Query like in this example) for use in a shortcode or with a filter on the_content.

The following code that uses object buffering works, but I've read in other places that buffering can be inefficient. I've seen HEREDOC too, but I don't see how that would work here unless I saved every template tag as a variable first (which seems inefficient again).

So my question is, what's the best way to return the output of a loop?

<?php if ( $cms_pl_pages->have_posts() ) :
ob_start(); // start object buffering. we'll run the loop and spit out final contents.
echo '<section class="cms-pl-gallery">';
while ( $cms_pl_pages->have_posts() ) : $cms_pl_pages->the_post();
    <article class="cms-pl-item clearfix">
        <?php has_post_thumbnail() ? the_post_thumbnail() : null; ?>
        <a href="<?php the_permalink(); ?>" title="Read '<?php the_title(); ?>.'">
            <h2><?php the_title(); ?></h2>
        <?php has_excerpt() ? the_excerpt() : null; ?>

<?php endwhile;
echo '</section> <!-- end .cms-pl-gallery -->';
$content = ob_get_contents(); // set $content to buffered object
ob_end_clean(); // throw away the buffered object
endif; wp_reset_postdata();
return $content; // return! ?>
share|improve this question
I don't think output buffering is a significant performance issue. There is some extra overhead to store the content in memory, but it's not going to be noticeable for a typical post and its markup. Also, keep in mind that using a caching plugin makes any performance hit a non-issue. It's still important to think about efficiency, but it's more important to write maintainable code. So, output buffering is definitely preferable to HEREDOC comments or other ugly hacks. – Ian Dunn Sep 13 '12 at 15:48
up vote 6 down vote accepted

There are replacements that return pure strings for all parts, no need to print anything into an output buffer. I like sprintf() and would write your example like this:

if ( $cms_pl_pages->have_posts() )
    $content = '<section class="cms-pl-gallery">';
    while ( $cms_pl_pages->have_posts() )
        $content .= sprintf(
            '<article class="cms-pl-item clearfix">
                    <a href="%2$s" title="Read %3$s">%4$s</a>
            apply_filters( 'the_permalink', get_permalink() ),
            the_title_attribute( array( 'echo' => FALSE ) ),
            the_title( '', '', FALSE ),
            has_excerpt() ? apply_filters( 'the_excerpt', get_the_excerpt() ) : ''
    $content .= '</section> <!-- end .cms-pl-gallery -->';
return $content;
share|improve this answer

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