File goes here: ~/Library/Application Support/Herd/config/valet/Drivers/MultisiteValetDriver.php

MultisiteValetDriver.php

<?php

namespace Valet\Drivers\Custom;

use Valet\Drivers\Specific\WordPressValetDriver;

class MultisiteValetDriver extends WordPressValetDriver
{
    /**
     * Get the fully resolved path to the application's front controller.
     */
    public function frontControllerPath(string $sitePath, string $siteName, string $uri): ?string
    {
        $uri = $this->rewriteMultisite($sitePath, $uri);
        return parent::frontControllerPath(
            $sitePath,
            $siteName,
            $this->forceTrailingSlash($uri)
        );
    }

    /**
     * Determine if the incoming request is for a static file.
     */
    public function isStaticFile(string $sitePath, string $siteName, string $uri)/*: string|false */
    {
        $uri = $this->rewriteMultisite($sitePath, $uri);
        return parent::isStaticFile($sitePath, $siteName, $uri);
    }

    /**
     * Determine if the driver serves the request.
     */
    public function serves(string $sitePath, string $siteName, string $uri): bool
    {
        return $this->isMultisite($sitePath) && parent::serves($sitePath, $siteName, $uri);
    }

    /**
     * Redirect to uri with trailing slash.
     */
    private function forceTrailingSlash($uri): ?string
    {
        if (substr($uri, -1 * strlen('/wp-admin')) === '/wp-admin') {
            header('Location: '.$uri.'/');
            exit;
        }

        return $uri;
    }

    /**
     * Determine if the application is Multisite.
     */
    private function isMultisite(string $sitePath): bool
    {
        $config = file_get_contents($sitePath.'/wp-config.php');
        return (bool) preg_match("/define\(\s*('|\")MULTISITE\\1\s*,\s*true\s*\)/mi", $config);
    }

    /**
     * Imitate the rewrite rules for a multisite .htaccess.
     */
    private function rewriteMultisite(string $sitePath, string $uri): string
    {
        if (preg_match('#^(/[^/]+)?(?!/wp-json)(/wp-.*)#', $uri, $matches) || preg_match('#^(/[^/]+)?(/.*\.php)#', $uri, $matches)) {
            return $matches[2];
        }
        return $uri;
    }
}