Wordpress post field validation (Change post status to draft if post is not complete)

functions.php

<?php
/**
 * Change post status to draft if post is not complete
 * @param  integer $post_id Post ID
 * @param  object $post    Post Object
 * @author Mostafa Soufi <mostafa.soufi@hotmail.com>
 */
function validate_post_field($post_id, $post) {
	// Check post status
	if( $post->post_status != 'publish' )
		return;

	// Check post title
	if( !$post->post_title ) {
		// Update post status to draft
		draft_post($post_id);
	}

	// Get category
	$category = get_the_category($post_id);

	// Check category
	if( count($category) >= 1 and $category[0]->term_id == 1) {
		// Update post status to draft
		$this->draft_post($post_id);
	}

	// Get tags
	$tags = get_the_tags($post_id);

	// Check tags
	if( !$tags ) {
		// Update post status to draft
		$this->draft_post($post_id);
	}
}

/**
 * Change post status to draft
 * @param  integer $post_id Post ID
 */
function draft_post($post_id) {
	// Update post
	$post = array(
		'ID'		=> $post_id,
		'post_status'	=> 'draft',
	);

	// Update the post into the database
	wp_update_post( $post );
}