How can I output the HTML of a query loop to a variable?

The issue you’re facing is likely due to the behavior of the_permalink() and the_title(). Both functions output directly to the page rather than returning values that can be captured into a variable, which can conflict with ob_start() and prevent capturing the HTML correctly.

To solve this, you need to use the functions that return values (e.g., get_permalink() and get_the_title()) instead of the ones that echo output directly (e.g., the_permalink() and the_title()).

Here’s a corrected version of your function:

function onepost() {

    // Set up the query arguments
    $args = array(
        'post_status'    => 'publish',
        'orderby'        => 'date',
        'order'          => 'DESC',
        'post_type'      => 'post',
        'posts_per_page' => 1,
    );

    // Start output buffering
    ob_start();

    // Run the query
    $query = new WP_Query( $args );

    // Check if the query has posts
    if ($query->have_posts()) :
        while ($query->have_posts()) : $query->the_post();
            // Capture the post permalink and title
            echo '<a href="' . get_permalink() . '">' . get_permalink() . '</a><br />';
            echo get_the_title(); // Output the title of the post
        endwhile;
    endif;

    // Get the contents of the buffer
    $theoutput = ob_get_contents();

    // Clean (flush) the buffer and turn it off
    ob_end_clean();

    // Return the captured HTML content
    return $theoutput;
}

Let me know if this works or if you need further clarification!

Thanks for the example, but it doesn’t work; echo $theoutput; shows nothing and var_dump($theoutput); is null.

This works:

$args = array(
        'post_status' => 'publish',
	'orderby' => 'date',
	'order' => 'DESC',
	'post_type' => 'post',
        'posts_per_page' => 1,
);
$query = new WP_Query( $args );

ob_start();

 while($query->have_posts()) : $query->the_post();
      the_permalink(); echo'<br />';
      the_title();
  endwhile; wp_reset_postdata();

$out = ob_get_clean();

echo $out;