html_excerpt.php

<?php
function custom_excerpt($custom_excerpt__arg) {
    global $post;
    $raw_excerpt = $custom_excerpt__arg;
    if ( '' == $custom_excerpt__arg ) {
        $custom_excerpt__arg = get_the_content('');
        $custom_excerpt__arg = strip_shortcodes( $custom_excerpt__arg );
        $custom_excerpt__arg = apply_filters('the_content', $custom_excerpt__arg);
        $custom_excerpt__arg = str_replace(']]>', ']]>', $custom_excerpt__arg);
        // runs function to only allow certain tags in the excerpt
        // $custom_excerpt__arg = strip_tags($custom_excerpt__arg, custom_excerpt__allowedtags());

        // set the excerpt word count and only break after sentence is complete
        $excerpt_word_count = 60;
        $excerpt_length = apply_filters('excerpt_length', $excerpt_word_count); 
        $tokens = array();
        $excerptOutput = '';
        $count = 0;

        // parse the excerpt into tokens; HTML tags, or words, followed by any whitespace
        preg_match_all('/(<[^>]+>|[^<>\s]+)\s*/u', $custom_excerpt__arg, $tokens);
        
        // function to find and include the rest of a sentence if the excerpt ends mid-sentence
        foreach ($tokens[0] as $token) { 
            if ($count >= $excerpt_word_count && preg_match('/[\?\.\!]\s*$/uS', $token)) { 
                // limit reached, continue until , ; ? . or ! occur at the end
                $excerptOutput .= trim($token);
                break;
            }
            $count++;  // add words to complete sentence
            $excerptOutput .= $token;  // append what's left of the token
        }

        $custom_excerpt__arg = trim(force_balance_tags($excerptOutput));  // update excerpt to complete sentences
        /*
        // set output at the end of the excerpt
        $excerpt_end = '<a class="read-more" alt= "' . get_the_title() . '" href="'. esc_url( get_permalink() ) . '">' . sprintf(__( 'Read more >' ), get_the_title()) . '</a>'; 
        $excerpt_more = apply_filters('excerpt_more', ' ' . $excerpt_end); 
        $pos = strrpos($custom_excerpt__arg, '</');
        if ($pos !== false) {
            $custom_excerpt__arg = substr_replace($custom_excerpt__arg, $excerpt_end, $pos, 0);  // inside last HTML tag, add $excerpt_end next to last word
        } else {
            $custom_excerpt__arg .= $excerpt_end;  // after the excerpt content, add $excerpt_end in new paragraph   
        }*/

        return $custom_excerpt__arg; 
    }

    return apply_filters('custom_excerpt', $custom_excerpt__arg, $raw_excerpt);
}

remove_filter('get_the_excerpt', 'wp_trim_excerpt');
add_filter('get_the_excerpt', 'custom_excerpt');

function custom_excerpt__allowedtags() {
    // tags allowed in the excerpt when custom_excerpt() is called
    return '<script>,<style>,<br>,<em>,<i>,<ul>,<ol>,<li>,<a>,<p>,<img>,<video>,<audio>,<strong>,<pre>,<blockquote>'; 
}