PHP: WordPress modified wp_trim_words to include tags

custom_trim_words.php

<?php

// Custom Excerpt
function custom_trim_words( $text, $num_words = 55, $more = null ) {
    if ( null === $more )
        $more = __( '&hellip;' );

    $original_text = $text;
    $text = strip_shortcodes( $text );
    // Add tags that you don't want stripped
    $text = strip_tags( $text, '<strong>, <b>, <em>, <i>' );

    if ( 'characters' == _x( 'words', 'word count: words or characters?' ) && preg_match( '/^utf\-?8$/i', get_option( 'blog_charset' ) ) ) {
        $text = trim( preg_replace( "/[\n\r\t ]+/", ' ', $text ), ' ' );
        preg_match_all( '/./u', $text, $words_array );
        $words_array = array_slice( $words_array[0], 0, $num_words + 1 );
        $sep = '';
    } else {
        $words_array = preg_split( "/[\n\r\t ]+/", $text, $num_words + 1, PREG_SPLIT_NO_EMPTY );
        $sep = ' ';
    }

    if ( count( $words_array ) > $num_words ) {
        array_pop( $words_array );
        $text = implode( $sep, $words_array );
        $text = $text . $more;
    } else {
        $text = implode( $sep, $words_array );
    }

    return apply_filters( 'custom_trim_words', $text, $num_words, $more, $original_text );
}

If this splits on an element, say middle of an <a> tag this absolutely destroys the layout. For example, if using this inside of a loop and you trim the excerpt mid <a> tag, all of the following elements will be nested inside this one.

Thanks @FernE97 working!