T5 Lazy Title UpdatesFill missing post titles from content when a post is called

lazy-title-updates.php

<?php
/**
 * Plugin Name: T5 Lazy Title Updates
 * Description: Fill missing post titles from content when a post is called
 * Plugin URI:
 * Version:     2013.01.08.02
 * Author:      Fuxia Scholz
 * Licence:     MIT
 * License URI: http://opensource.org/licenses/MIT
 */

add_action( 'the_post', 't5_lazy_title_update' );
add_action( 'save_post', 't5_lazy_title_update_save', 10, 2 );

/**
 * Add a title when the post is called in setup_postdata().
 *
 * @wp-hook the_post
 * @param   object $post
 * @return  void
 */
function t5_lazy_title_update( $post )
{
	if ( ! empty ( $post->post_title )
		and strip_shortcodes( $post->post_title ) === $post->post_title
		)
		return;

	$clean_content = wp_strip_all_tags( $post->post_content, TRUE );
	$clean_content = strip_shortcodes( $clean_content );

	if ( '' === $clean_content )
		return;

	$words = preg_split( "/\s+/", $clean_content, 40, PREG_SPLIT_NO_EMPTY );
	$title = implode( ' ', $words );
	$title = rtrim( $title, '.;,*' );
	$slug  = wp_unique_post_slug(
		sanitize_title_with_dashes( $title ),
		$post->ID,
		$post->post_status,
		$post->post_type,
		$post->post_parent
	);

	wp_update_post(
		array (
			'ID'         => $post->ID,
			'post_title' => $title,
			'post_name'  => $slug
		)
	);

	// $post is passed by reference, so we update this property in realtime
	$post->post_title = $title;
	$post->post_name  = $slug;
}

/**
 * Fill title from post content on save
 *
 * @wp-hook save_post
 * @param   int $post_ID
 * @param   object $post
 * @return  void;
 */
function t5_lazy_title_update_save( $post_ID, $post )
{
	t5_lazy_title_update( $post );
}

This works like a wonder. I seriously recommend you to publish this to the official WordPress repository as there is no plugin like this and would be a great help to many, specially when importing from Tumblr.

this is exactly what i need but "how to set maximum post title length" with this? help will be appreciated..

Thanks for this. Didn't have the exact same issue you fixed with your code, but it gave me a point in the right direction.