function summarise( $input, $break = " ", $end_text = "...", $limit = 255, $tidy_html = 1, $strip_html = 0 ) {
               if ( strlen( $input ) >= $limit ) {
                       $breakpoint = strpos( $input, $break, $limit );
                       $input = substr( $input, 0, $breakpoint ) . $end_text;
               }
               if ( $tidy_html == 1 ) {
                       ob_start(  );
                       $tidy = new tidy;
                       $config = array( 'indent' => true, 'output-xhtml' => true, 'wrap' => 200, 'clean' => true, 'show-body-only' => true );
                       $tidy->parseString( $input, $config, 'utf8' );
                       $tidy->cleanRepair(  );
                       $input = $tidy;
               }
               if ( $strip_html == 1 ) {
                       $input = strip_tags( $input );
               }
               return $input;
}

https://css-tricks.com/snippets/php/truncate-strings/

Shorten text while preserving the HTML tags. Useful for news and articles preview.

Shorten HTML text

PHP