Reply To: Triggering the Advanced Custom Fields (ACF) \'acf/save_post\' Action

• aspsa

• March 1, 2021 at 11:24 am

I appreciate the reply, John. Here is the full ‘acf/save_post’ description from :

Fires when saving the submitted $_POST data.

This action allows you to hook in before or after the $_POST data has been saved, making it useful to perform additional functionality when updating (emphasis mine) a post or other WP object.

Digging deeper, I ran a search for the the “acf/save_post” WordPress “add_action” action hook, which took me to the file “..\plugins\advanced-custom-fields\includes\acf-form-functions.php”. Here is a code excerpt from this file:

/**
 * _acf_do_save_post
 *
 * Private function hooked into 'acf/save_post' to actually save the $_POST data.
 * This allows developers to hook in before and after ACF has actually saved the data.
 *
 * @date	11/1/19
 * @since	5.7.10
 *
 * @param	int|string $post_id The post id.
 * @return	void
 */
function _acf_do_save_post( $post_id = 0 ) {
	
	// Check and update $_POST data.
	if( $_POST['acf'] ) {
		acf_update_values( $_POST['acf'], $post_id );
	}	
}

// Run during generic action.
add_action( 'acf/save_post', '_acf_do_save_post' );

The “acf_update_values” function is located in the file “..\plugins\advanced-custom-fields\includes\acf-value-functions.php” in the following code excerpt:

/**
 * acf_update_values
 *
 * Updates an array of values.
 *
 * @date	26/2/19
 * @since	5.7.13
 *
 * @param	array values The array of values.
 * @param	(int|string) $post_id The post id.
 * @return	void
 */
function acf_update_values( $values, $post_id ) {
	
	// Loop over values.
	foreach( $values as $key => $value ) {
		
		// Get field.
		$field = acf_get_field( $key );
		
		// Update value.
		if( $field ) {
			acf_update_value( $value, $post_id, $field );
		}
	}
}

The “foreach” loop invokes the “acf_update_value” function that is located in the same PHP file. Here is its code excerpt:

/**
 * acf_update_value
 *
 * Updates the value for a given field and post_id.
 *
 * @date	28/09/13
 * @since	5.0.0
 *
 * @param	mixed $value The new value.
 * @param	(int|string) $post_id The post id.
 * @param	array $field The field array.
 * @return	bool.
 */
function acf_update_value( $value, $post_id, $field ) {
	
	// Allow filter to short-circuit update_value logic.
	$check = apply_filters( "acf/pre_update_value", null, $value, $post_id, $field );
	if( $check !== null ) {
		 return $check;
	}
    
    /**
	 * Filters the $value before it is updated.
	 *
	 * @date	28/09/13
	 * @since	5.0.0
	 *
	 * @param	mixed $value The value to update.
	 * @param	string $post_id The post ID for this value.
	 * @param	array $field The field array.
	 * @param	mixed $original The original value before modification.
	 */
	$value = apply_filters( "acf/update_value", $value, $post_id, $field, $value );
	
	// Allow null to delete value.
	if( $value === null ) {
		return acf_delete_value( $post_id, $field );
	}
	
	// Update meta.
	$return = acf_update_metadata( $post_id, $field['name'], $value );
	
	// Update reference.
	acf_update_metadata( $post_id, $field['name'], $field['key'], true );
	
	// Delete stored data.
	acf_flush_value_cache( $post_id, $field['name'] );
	
	// Return update status.
	return $return;
}

The relevant line of code is the “acf_update_metadata” statement located just below the “// Update reference.” comment. In the interest of reducing this post’s size:

The “acf_update_metadata” function is in the “..\acf-meta-functions.php” file. One of last code lines invokes the “update_metadata” function that is located in the “..\meta.php” file.

The “update_metadata” function includes the following “do_action”, which according to the code comments “fires immediately before updating a post’s metadata”:

do_action( "update_postmeta', $meta_id, $object_id, $meta_key, $meta_value' );

According to this sequence of function invocations, when I edit an ACF custom field in a post’s editor and then click the ‘Update’ button to update the post’s value in the WordPress database’s post table, this triggers a sequence of events that includes updating the WordPress post metadata table.

In actually, neither the post metadata table is update nor does

add_action('save_post', 'my_save_post');

appear to be invoked from

do_action( "update_postmeta', $meta_id, $object_id, $meta_key, $meta_value' );

Perhaps, I’ve missed something. Again, your feedback is appreciated.