This sends the content to http://filip.journet.sdu.dk/berta/api.php, retrieves its LIX and stores it in a custom field.

WP - Get content LIX

/*
 * GET SAVED LIX BY ID
 */
if ( !function_exists( 'get_lix' ) ) {
	function get_lix( $id = NULL ) {
		global $post;
		if ( is_user_logged_in() && !is_home() && !is_front_page() ) {
			if ( empty( $id ) && is_object( $post ) ) {
				$id = $post->ID;
			}
			return '<small>'. __('Word count','lix') .': '. get_post_meta( $id, 'text_word', true ) .'<br/>'. __('LIX','lix') .': '. get_post_meta( $id, 'text_lix', true ) .'</small>';
		}
	}
	/* USE LIKE SO
	 * echo get_lix( 101 );
	 */
}

/*
 * SAVE LIX
 * Thanks to @fiwa and http://filip.journet.sdu.dk/berta/api
 */
if ( !function_exists( 'save_lix' ) ) {
	function save_lix() {
		global $post;
		if ( is_object( $post ) ) {
			$text = $post->post_content;
			
			// these may be unneccecary, but let's sanitize the content anyway
			$text = strip_shortcodes( $text );
			$text = strip_tags( $text );
			$text = str_replace( array(' ','&nbsp;'), '%20', $text );
			$text = str_replace( array(',',';','"',':','-','!','?',"'"), '', $text );
			
			// æøå may cause confusion, so let's replace it with a single letter
			$text = str_replace( array('Æ','æ','Ø','ø','Å','å'), 'o', $text );
			
			// & is a word
			$text = str_replace( '&', 'og', $text );
			
			// let's just remove these so we're in the clear
			$text = str_replace( array("\r\n", "\r", "\n"), "%20", $text );
			
			$text = urlencode( $text );
			$json = json_decode( file_get_contents( 'http://filip.journet.sdu.dk/berta/api.php?broedtekst='. $text ) );
			
			$ord  = round( $json->berta->antal_ord );
			if ( !empty( $ord ) ) {
				update_post_meta( $post->ID, 'text_word', $ord );
			}
			
			$lix  = round( $json->berta->lix );
			if ( !empty( $lix ) ) {
				update_post_meta( $post->ID, 'text_lix', $lix );
			}
			
			// now the LIX is saved and we can retrieve it later with get_lix();
		}
	}
	add_action('save_post',          'save_lix');
//	add_action('draft_to_publish',   'save_lix');
//	add_action('new_to_publish',     'save_lix');
//	add_action('pending_to_publish', 'save_lix');
//	add_action('future_to_publish',  'save_lix');
}