Limit subsite based on page visit

code.php

<?php

/**
 * Set MS_SUBSITE_MAX_HIT as limit of page visit
 */
if( ! defined( 'MS_SUBSITE_MAX_HIT' ) ) define( 'MS_SUBSITE_MAX_HIT', 5 );

add_action( 'shutdown', function() {
    
    // Exclude main site
    if( is_main_site() ) return;
    
    // Exclude super admin visit
    //if( is_super_admin() ) return;
    
    // Exclude visit of admin dashboard
    if( is_admin() ) return;
    
    // Get existing visit count
    $counter = ( int ) get_site_option( 'ms_site_counter' );
    
    // Increase by 1
    $counter++;
    
    // Update with new counter
    update_site_option( 'ms_site_counter', $counter );
    
} );

add_action( 'template_redirect', function() {
    
    if( is_main_site() ) return;
    
    // Get existing visit count
    $counter = ( int ) get_site_option( 'ms_site_counter' );
    
    if( $counter > MS_SUBSITE_MAX_HIT )
    {
        switch_to_blog( 1 );
        wp_redirect( site_url() );
        exit;
    }
    
} );

add_action( 'admin_notices', function() {
    
    // Get existing visit count
    $counter = ( int ) get_site_option( 'ms_site_counter' );
    
    if( $counter > MS_SUBSITE_MAX_HIT )
    {
    ?>
    <div class="notice notice-error is-dismissible">
        <p>Your site visits have reached it's limit, please contact the administrator.</p>
    </div>
    <?php
    }
} );