add_action insert html

Question

I know I am missing something simple. I am trying to use html to log to footer to learn wp. In theme functions.php:

function myLog() {
    echo 'test';    
}

In theme footer within the .siteInfo div:

<?php add_action( 'wpmu_new_blog', 'myLog' );?>

when a new user creates a new site myLog should output html 'test'?

Please help, save me many more hours of reading and trials.

Answer 1

If you want something to display in the footer, you first need to hook it into the footer to display it. So that would look like this:

function myLog() {
    echo 'test';
}
add_action('wp_footer','myLog');

However, this is not at all connected to the data you want, which is when a new user creates a new site. The wpmu_new_blog action is deprecated so use the wp_initialize_site hook instead.

When this hook fires, it will not output information into the footer because it's processing information. So really, this step is just saving the information somewhere.

/**
 * Function for `wp_initialize_site` action-hook.
 * 
 * @param WP_Site $new_site New site object.
 * @param array   $args     Arguments for the initialization.
 *
 * @return void
 */
function saveLog( $new_site, $args ) {
    // Do something
}
add_action('wp_initialize_site','saveLog',20,2);

Since there are two events happening, that's why you need to access two hooks. So to put it all together (this is untested, I'm literally just writing this code here)

/**
 * Function for `wp_initialize_site` action-hook.
 * 
 * @param WP_Site $new_site New site object.
 * @param array   $args     Arguments for the initialization.
 *
 * @return void
 */
function saveLog( $new_site, $args ) {

    // Get the info from the newly created site
    $newInfo = array(array(
        'blog_id' => $new_site->get('id'),
        'domain' => $new_site->get('domain')
    ));

    //Get previous log info from the Transients API
    $log = get_transient('new_site_log');
    if(is_array($log)) {
        //Merge if it exists
        $log = array_merge($log,$newInfo); 
    } else {
        //Set new if it doesn't
        $log = $newInfo;
    }
    
    //Save the log to the Transients API
    set_transient('new_site_log',$log,DAY_IN_SECONDS);
}
add_action('wp_initialize_site','saveLog',20,2);

function myLog() {
    //Get the log info from the Transients API
    $log = get_transient('new_site_log');

    //If an array with stuff, loop through it
    if(is_array($log) && count($log)) {
        echo '<ol>';
        foreach($log as i => $siteInfo) {
            // Echo the info we saved
            printf(
                '<li>Blog ID: %s<br />Domain: %s</li>', 
                $siteInfo['blog_id'], 
                $siteInfo['domain']
            );   
        }
        echo '</ol>';
    } else {
        echo 'No new sites were created';
    }
}
add_action('wp_footer','myLog');

This example uses the Transients API to save the info and transients expire, but you can use whatever.

Answer 2

Write myLog() in theme footer within the .siteInfo div. It will work.