Replacing WordPress content with an excerpt without editing theme files

Let’s suppose our front page and archives used the WordPress function <?php the_content(); ?> to retrieve all post content. Let’s further suppose we’re want to modify this with a child theme to show excerpts instead of the entire post.

We could easily just change <?php the_content(); ?> to <?php the_excerpt(); ?>.

But, We don’t want to edit the core files at all. We want to be able to upgrade our theme without our modifications being broken.

The Solution is:

WordPress filters.

In our child theme’s functions.php file, We added this bit of PHP:

// Add filter to the_content
add_filter('the_content', 'my_excerpts');
This tells WP that we want to filter the_content() with our own function.

Here’s what that function looks like:

function my_excerpts($content = false) {

// If is the home page, an archive, or search results
if(is_front_page() || is_archive() || is_search()) :
global $post;
$content = $post->post_excerpt;

// If an excerpt is set in the Optional Excerpt box
if($content) :
$content = apply_filters('the_excerpt', $content);

// If no excerpt is set
else :
$content = $post->post_content;
$excerpt_length = 55;
$words = explode(' ', $content, $excerpt_length + 1);
if(count($words) > $excerpt_length) :
array_pop($words);
array_push($words, '...');
$content = implode(' ', $words);
endif;
$content = '<p>' . $content . '</p>';

endif;
endif;

// Make sure to return the content
return $content;

}

Now, we’ve changed the instances of the_content() that we want to excerpts. This example doesn’t strip the tags of the excerpt like the default WordPress function, but we can easily change that by changing this line:

$content = $post->post_content;
to:
$content = $post->post_content;
$content = strip_shortcodes($content);
$content = str_replace(']]>', ']]>', $content);
$content = strip_tags($content);

There may be a better way to filter the_content(), and we’d love to see what you can come up with if so.

Related articles:

• Replace wordpress Content in PRE Tags with HTML Entities
• Showing the post password form for excerpts in WordPress
• Using wordpress shortcodes to show members-only content
• Automatically insert content after each wordpress post
• Display most popular content in wordpress sidebar