Read more that ends in sentence or exact words.

excerpt.php

<?php
add_filter( 'the_content', 'my_the_content_filter', 22 );
function my_the_content_filter( $content ) {
    

    if ( is_home() || is_archive() || is_search() ){

        // Mode word
        $mode = 'sentence'; // word or sentence
        $count = 11;

        // Let WP do its thing
        $trimmed = wp_trim_words(
            $content, 
            1000000, 
            ''
        );

        // Split trimmed content into x number of words
        $words = explode(' ', $trimmed);
        $words = array_slice($words, 0, $count);
        $content = implode(' ', $words);

        if($mode==='sentence'){
            $pos = mb_strlen($content); // Find last word position
            $pos = mb_strpos($trimmed, '.', $pos-1); // Find the period(.)
            // TODO: Support other end of sentence marks like ? and !
            if($pos!==false){
                $content = mb_substr($trimmed, 0, $pos+1); // Get string until end of sentence
            }
        }
        
        $content .= sprintf(
            '<p><a class="btn btn-default read-more" href="%s" title="%s">%s</a></p>',
            get_permalink(), get_the_title(), 'Read More'
        );
        
    }

    // Returns the content.
    return $content;
}