Run a function when a new site is created in Wordpress Multisite

Question

I am currently developing a multi-site plug-in for WordPress. I need to run a function when a new site is created.

Answer 1

I guess you are looking for an action/filter.

wpmu_new_blog this action is fired in wpmu_create_blog function (wp-includes/ms-functions.php)

do_action( 'wpmu_new_blog', $blog_id, $user_id, $domain, $path, $site_id, $meta );

Answer 2

Since WP 5.1.0, wpmu_new_blog has been deprecated in favour of wp_insert_site:

/**
 * Fires once a site has been inserted into the database.
 *
 * @since 5.1.0
 *
 * @param WP_Site $new_site New site object.
 */
do_action( 'wp_insert_site', $new_site );

Use it like this in your plugin or theme:

add_action('wp_insert_site', function($site) {
  // do something
});

A good place to look for available hooks is wp-includes/ms-default-filters.php

wp_insert_site on WordPress Developer Handbook