save_post │ action-hook │ WP 1.5.0

Fires whenever a post or page is created or updated, including publication through import, XML-RPC, or email.

Post data is passed in the second $post parameter, but it can also usually be obtained through $_POST, $_GET, or the global global $post_data variable. Which source is available depends on how the post is edited. Quick Edit, for example, uses $_POST.

// Clear the post cache
clean_post_cache( $post_ID );

do_action( "save_post_{$post->post_type}", $post_ID, $post, $update );

Usage

add_action( 'save_post', 'wp_kama_save_post_action', 10, 3 );

/**
 * Function for `save_post` action-hook.
 * 
 * @param int     $post_id Post ID.
 * @param WP_Post $post    Post object.
 * @param bool    $update  Whether this is an existing post being updated.
 *
 * @return void
 */
function wp_kama_save_post_action( $post_id, $post, $update ){

	// action...
}

$post_id(int)

ID of the post being updated.

$post(object)

The post object being updated. It is the same type of object normally stored in the global $post variable.

$update(bool)

true when an existing post is updated.
false when a new post is added.

Examples

#1 Send an email when a post is updated

This demonstration sends the site administrator an email notification whenever a post is updated:

add_action( 'save_post', 'my_project_updated_send_email' );
function my_project_updated_send_email( $post_id ) {

	// Do not send an email for revisions
	if ( wp_is_post_revision( $post_id ) || get_post($post_id)->post_status != 'publish' )
		return;

	$post_title = get_the_title( $post_id );
	$post_url = get_permalink( $post_id );
	$subject = 'A post was updated';

	$message = "The following post was updated on your site:\n\n";
	$message .= $post_title . ": " . $post_url;

	// Send the email.
	wp_mail( get_option('admin_email'), $subject, $message );
}

#2 The custom book post type

Suppose you have a book post type and need to add information about the author, publisher, and print availability. This code demonstrates how to store those values in post metadata:

/**
 * Saves post metadata when the post is saved.
 */
add_action( 'save_post', 'save_book_meta' );
function save_book_meta( $post_id ) {
	// Define the slug once and reuse it throughout code related
	// to the post type, as is customary in classes
	$slug = 'book';

	// Check the post type and return if it is not book.
	if ( $slug != $_POST['post_type'] )
		return;

	// Update post metadata.

	if ( isset( $_REQUEST['book_author'] ) ) {
		update_post_meta( $post_id, 'book_author', sanitize_text_field( $_REQUEST['book_author'] ) );
	}

	if ( isset( $_REQUEST['publisher'] ) ) {
		update_post_meta( $post_id, 'publisher', sanitize_text_field( $_REQUEST['publisher'] ) );
	}

	// inprint is a checkbox.
	if ( isset( $_REQUEST['inprint'] ) ) {
		update_post_meta( $post_id, 'inprint', TRUE );
	} else {
		update_post_meta( $post_id, 'inprint', FALSE );
	}
}

In this example, the if ( $slug != $_POST['post_type'] ) check can be replaced by using the save_post_book event instead of save_post.

#3 Avoid an infinite loop

Calling wp_update_post() inside the save_post event causes an infinite loop because wp_update_post() invokes save_post. To prevent this, remove the attached hook before calling wp_update_post(), then add it again afterward:

// This function makes all posts in the default category private
add_action( 'save_post', 'set_private_categories' );
function set_private_categories( $post_id ){
	// Obtain the real post ID if this is a revision
	if ( $parent_id = wp_is_post_revision( $post_id ) )
		$post_id = $parent_id;

	// Obtain the default category ID from the options
	$defaultcat = get_option( 'default_category' );

	// Check whether the post is in the default category
	if ( in_category( $defaultcat, $post_id ) ) {
		// Remove the hook to prevent an infinite loop
		remove_action( 'save_post', 'set_private_categories' );

		// Update the post. The save_post event fires at this point
		wp_update_post( array( 'ID' => $post_id, 'post_status' => 'private' ) );

		// Add the hook back
		add_action( 'save_post', 'set_private_categories' );
	}
}

This part of the code is required:

// Remove the hook to prevent an infinite loop
remove_action( 'save_post', 'set_private_categories' );

// Update the post. The save_post event fires at this point
wp_update_post( array( 'ID' => $post_id, 'post_status' => 'private' ) );

// Add the hook back
add_action( 'save_post', 'set_private_categories' );