WordPress excerpt without plugin

<?php add_filter('the_excerpt', 'my_excerpts');
function my_excerpts($content = false) {
            global $post;
            $mycontent = $post->post_excerpt;
            $mycontent = $post->post_content;
            $mycontent = strip_shortcodes($mycontent);
            $mycontent = str_replace(']]>', ']]&gt;',$mycontent);
            $mycontent = strip_tags($mycontent);
            $excerpt_length = 55;
            $words = explode(' ', $mycontent,$excerpt_length + 1);
            if(count($words) > $excerpt_length) :
                array_pop($words);
                array_push($words, '...');
                $mycontent = implode(' ', $words);
            endif;
            $mycontent = '<p>' . $mycontent . '</p>';
// Make sure to return the content
    return $mycontent;
}
?>