Display excerpt with some tags

gistfile1.aw

<?php
/* Used to display the excerpt of a post across the site. Written very closely with
 * wp_trim_excerpt, but instead of stripping out all tags, we want to make sure that
 * some basic style still remains as this display function will be used for the index
 * and archive templates, not something as plain as a feed or meta description. */
function prefix_display_excerpt( $number_of_words = 55 ) {
	global $post;
	$content = get_the_content();
	$content = strip_shortcodes( $content );
	$content = preg_replace( '@<(script|style)[^>]*?>.*?</\\1>@si', '', $content );
	$content = strip_tags( $content, '<p><a><em><strong><del>' );

	/* Continue to provide a way for child themes to modify the excerpt
	 * length and use of ellipsis */
	$excerpt_length = apply_filters( 'excerpt_length', $number_of_words );
	$excerpt_more = apply_filters( 'excerpt_more', ' ' . '[...]' );
	
	$words_array = preg_split( "/[\n\r\t ]+/", $content, $excerpt_length + 1, PREG_SPLIT_NO_EMPTY );
	if ( count( $words_array ) > $excerpt_length ) {
		array_pop( $words_array );
		$content = implode( ' ', $words_array );
		$content = $content . $excerpt_more;
	} else {
		$content = implode( ' ', $words_array );
	}

	echo force_balance_tags( $content ) . ' <a href="'. get_permalink( get_the_ID() ) . '">read more</a>';
}