Usage

Using Action Scheduler requires:

1. installing the library
2. scheduling an action

Installation

There are two ways to install Action Scheduler:

1. regular WordPress plugin; or
2. a library within your plugin’s codebase.

Note that Action Scheduler follows an L-2 dependency version policy. That is, the library requires at least the “latest minus two” version of WordPress and the PHP minimum version requirement of that WordPress version.

Usage as a Plugin

Action Scheduler includes the necessary file headers to be used as a standard WordPress plugin.

To install it as a plugin:

1. Download the .zip archive of the latest stable release
2. Go to the Plugins > Add New > Upload administration screen on your WordPress site
3. Select the archive file you just downloaded
4. Click Install Now
5. Click Activate

Or clone the Git repository into your site’s wp-content/plugins folder.

Using Action Scheduler as a plugin can be handy for developing against newer versions, rather than having to update the subtree in your codebase. When installed as a plugin, Action Scheduler does not provide any user interfaces for scheduling actions. The only way to interact with Action Scheduler is via code.

Usage as a Library

To use Action Scheduler as a library:

1. include the Action Scheduler codebase
2. load the library by including the action-scheduler.php file

Using a subtree in your plugin, theme or site’s Git repository to include Action Scheduler is the recommended method. Composer can also be used.

To include Action Scheduler as a git subtree:

Step 1. Add the Repository as a Remote

git remote add -f subtree-action-scheduler https://github.com/woocommerce/action-scheduler.git

Adding the subtree as a remote allows us to refer to it in short from via the name subtree-action-scheduler, instead of the full GitHub URL.

Step 2. Add the Repo as a Subtree

git subtree add --prefix libraries/action-scheduler subtree-action-scheduler trunk --squash

This will add the trunk branch of Action Scheduler to your repository in the folder libraries/action-scheduler.

You can change the --prefix to change where the code is included. Or change the trunk branch to a tag, like 2.1.0 to include only a stable version.

Step 3. Update the Subtree

To update Action Scheduler to a new version, use the commands:

git fetch subtree-action-scheduler trunk
git subtree pull --prefix libraries/action-scheduler subtree-action-scheduler trunk --squash

Loading Action Scheduler

Regardless of how it is installed, to load Action Scheduler, you only need to include the action-scheduler.php file, e.g.

<?php
require_once( plugin_dir_path( __FILE__ ) . '/libraries/action-scheduler/action-scheduler.php' );

There is no need to call any functions or do else to initialize Action Scheduler.

When the action-scheduler.php file is included, Action Scheduler will register the version in that file and then load the most recent version of itself on the site. It will also load the most recent version of all API functions.

Load Order

Action Scheduler will register its version on 'plugins_loaded' with priority 0 - after all other plugin codebases has been loaded. Therefore the action-scheduler.php file must be included before 'plugins_loaded' priority 0.

It is recommended to load it when the file including it is included. However, if you need to load it on a hook, then the hook must occur before 'plugins_loaded', or you can use 'plugins_loaded' with negative priority, like -10.

Action Scheduler will later initialize itself on 'init' with priority 1. Action Scheduler APIs should not be used until after 'init' with priority 1. As described in API Function Availability, you can also use the 'action_scheduler_init' action hook for this purpose.

Usage in Themes

When using Action Scheduler in themes, it’s important to note that if Action Scheduler has been registered by a plugin, then the latest version registered by a plugin will be used, rather than the version included in the theme. This is because of the version dependency handling code using 'plugins_loaded' since version 1.0.

Scheduling an Action

To schedule an action, call the API function for the desired schedule type passing in the required parameters.

The example code below shows everything needed to schedule a function to run at midnight, if it’s not already scheduled:

require_once( plugin_dir_path( __FILE__ ) . '/libraries/action-scheduler/action-scheduler.php' );

/**
 * Schedule an action with the hook 'eg_midnight_log' to run at midnight each day
 * so that our callback is run then.
 */
function eg_schedule_midnight_log() {
	if ( false === as_has_scheduled_action( 'eg_midnight_log' ) ) {
		as_schedule_recurring_action( strtotime( 'tomorrow' ), DAY_IN_SECONDS, 'eg_midnight_log', array(), '', true );
	}
}
add_action( 'init', 'eg_schedule_midnight_log' );

/**
 * A callback to run when the 'eg_midnight_log' scheduled action is run.
 */
function eg_log_action_data() {
	error_log( 'It is just after midnight on ' . date( 'Y-m-d' ) );
}
add_action( 'eg_midnight_log', 'eg_log_action_data' );

Note that the as_has_scheduled_action() function was added in 3.3.0: if you are using an earlier version, you should use as_next_scheduled_action() instead. For more details on all available API functions, and the data they accept, refer to the API Reference.

Passing arguments

It is possible to pass arguments to your callbacks. When you initially supply the arguments via a call to as_schedule_single_action() or one of its sister functions, they should be in an array. However, your callback function will receive each array item as an individual parameter. Here’s an example:

// You must specify the number of arguments to be accepted (in this case, 2).
add_action( 'purchase_notification', 'send_purchase_notification', 10, 2 );

// When scheduling the action, provide the arguments as an array.
as_schedule_single_action( time(), 'purchase_notification', array(
    'bob@foo.bar',
    'Learning Action Scheduler (e-book)',
) );

// Your callback should accept the appropriate number of parameters (again, in this case, 2).
function send_purchase_notification( $customer_email, $purchased_item ) {
    wp_mail( 
        $customer_email,
        'Thank you!',
        "You purchased $purchased_item successfully."
    );
}

The above is a pretty simple illustration, and you would of course need to make changes if you wish to do anything more complex, such as accept a variable number of arguments. However, it hopefully illustrates the basic principles involved.