Show excerpt on front page using the_content(); and ACF - php

Question

I need to show a excerpt on my home page. I have standard post and a custom post type 'webinar'. The CPT 'webinar' has a custom field, using ACF 'webinar_description' that is a an equivalent of 'description' in normal posts.
I am able to display both, by adding a filter for the 'webinar_description' like this:
add_filter('the_content','add_my_custom_field');
function add_my_custom_field($data) {
$data .= get_field('webinar_description');
return $data;
}
Now I have both post types displaying, but it displays the entire 'description' or 'webinar_description' field. I need to trim it at 40 words and add a '... Read More' with 'Read More' being a link to the article.
I have tried this, but it only works on the normal 'post' type field 'description' it doesn't work on my 'webinar' custom post type -> custom field 'webinar-description'
<?php $content = get_the_content(); echo mb_strimwidth($content, 0, 400, '[Read more]');?>
How can I create a filter or function that will limit both to 400 (or whatever) characters and add the link?

Answer 1

Not sure if this will help anyone in a similar situation, but this is how I solved it. First, in functions.php make the custom post type available
function cpt_get_excerpt(){
$excerpt = get_field('webinar_description');
$excerpt = preg_replace(" (\[.*?\])",'',$excerpt);
$excerpt = strip_shortcodes($excerpt);
$excerpt = strip_tags($excerpt);
$excerpt = substr($excerpt, 0, 400);
$excerpt = substr($excerpt, 0, strripos($excerpt, " "));
$excerpt = trim(preg_replace( '/\s+/', ' ', $excerpt));
$excerpt = $excerpt.'... <a class="c-drkGold" href="'.get_permalink($post->ID).'">Read More</a>';
return $excerpt;
}
Then where you want to display it, use a if/else statement based on the post type and display accordingly (this example is from static front page).
<?php
if( get_post_type() == 'post' ) {
?><p class="l-nmb"><?php
$content = get_the_content(); echo mb_strimwidth($content, 0, 400, '... Read more'); ?> </p>
<?php } else {
?><p class="l-nmb"><?php
$content = cpt_get_excerpt(); echo mb_strimwidth($content, 0, 400, '... Read more'); ?> </p>
<?php } ?>