ajax – Sharing variables in each actions wp_footer and wp_ajax

I’ve some code in my features.php that, below a particular time situation, showes a popup that notices about some database replace routine. What is going on right here, is that when this situation occurs, I place html + script code in my footer by the wp_footer motion, that calls an ajax motion for beginning these updates. Due to this time situation and different stuffs, I’ve some variables that has the identical worth in wp_footer and in wp_ajax_update_db, so I wish to write these variables just one time for each the actions. That is my features.php like code

/**
 * Popup for html to point out replace progress
 */
add_action('wp_footer', perform() {
    $var1 = 'some worth';
    $var2 = 'some worth';
    $var3 = 'some worth';

    if( $timeCondition ){
        // My name to ajax update_db
        // Rendered Html
    }
}

/**
 * Engine for the replace routine
 */ 
add_action('wp_ajax_update_db', 'update_db');
add_action('wp_ajax_nopriv_update_db','update_db');
perform update_db() {
    $var1 = 'some worth';
    $var2 = 'some worth';
    $var3 = 'some worth';
    
    // Code for updating the dbs
}

I used to be pondering that I might wrap the wp_ajax_update_db contained in the wp_footer motion and declare the variables solely at first, however I do not know if that is the appropriate approach, like this

/**
 * Popup for html to point out replace progress
 */
add_action('wp_footer', perform() {
    $var1 = 'some worth';
    $var2 = 'some worth';
    $var3 = 'some worth';

    if( $timeCondition ){
        // My name to ajax update_db
        // Rendered Html

        /**
         * Engine for the replace routine
         */ 
        add_action('wp_ajax_update_db', 'update_db');
        add_action('wp_ajax_nopriv_update_db','update_db');
        perform update_db() {
            // Code for updating the dbs
        }

    }
}