Add --url parameter support to site create command

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>

Author: Copilot

src/Site_Command.php

@@ -389,8 +389,15 @@ public function delete( $args, $assoc_args ) {
 	 *
 	 * ## OPTIONS
 	 *
-	 * --slug=<slug>
+	 * [--slug=<slug>]
 	 * : Path for the new site. Subdomain on subdomain installs, directory on subdirectory installs.
+	 * Required if --url is not provided.
+	 *
+	 * [--url=<url>]
+	 * : Full URL for the new site. Use this to specify a custom domain instead of the auto-generated one.
+	 * For subdomain installs, this allows you to use a different base domain (e.g., 'http://site.example.com' instead of 'http://site.main.example.com').
+	 * For subdirectory installs, this allows you to use a different path.
+	 * If provided, --slug is optional and will be derived from the URL.
 	 *
 	 * [--title=<title>]
 	 * : Title of the new site. Default: prettified slug.
@@ -409,8 +416,17 @@ public function delete( $args, $assoc_args ) {
 	 *
 	 * ## EXAMPLES
 	 *
+	 *     # Create a site with auto-generated domain
 	 *     $ wp site create --slug=example
 	 *     Success: Site 3 created: http://www.example.com/example/
+	 *
+	 *     # Create a site with a custom domain (subdomain multisite)
+	 *     $ wp site create --url=http://site.example.com
+	 *     Success: Site 4 created: http://site.example.com/
+	 *
+	 *     # Create a site with a custom subdirectory (subdirectory multisite)
+	 *     $ wp site create --url=http://example.com/custom/path/
+	 *     Success: Site 5 created: http://example.com/custom/path/
 	 */
 	public function create( $args, $assoc_args ) {
 		if ( ! is_multisite() ) {
@@ -419,7 +435,56 @@ public function create( $args, $assoc_args ) {
 
 		global $wpdb, $current_site;
 
-		$base = $assoc_args['slug'];
+		// Check if either slug or url is provided
+		$has_slug = isset( $assoc_args['slug'] );
+		$has_url  = isset( $assoc_args['url'] );
+
+		if ( ! $has_slug && ! $has_url ) {
+			WP_CLI::error( 'Either --slug or --url must be provided.' );
+		}
+
+		// If URL is provided, parse it to get domain and path
+		$custom_domain = null;
+		$custom_path   = null;
+		$base          = null;
+
+		if ( $has_url ) {
+			$parsed_url = parse_url( $assoc_args['url'] );
+			if ( ! isset( $parsed_url['host'] ) ) {
+				WP_CLI::error( 'Invalid URL format. Please provide a valid URL (e.g., http://site.example.com).' );
+			}
+
+			$custom_domain = $parsed_url['host'];
+			$custom_path   = isset( $parsed_url['path'] ) ? $parsed_url['path'] : '/';
+
+			// Ensure path ends with /
+			if ( '/' !== substr( $custom_path, -1 ) ) {
+				$custom_path .= '/';
+			}
+
+			// Derive base/slug from the URL if not explicitly provided
+			if ( ! $has_slug ) {
+				if ( is_subdomain_install() ) {
+					// For subdomain installs, use the first part of the domain as the base
+					$domain_parts = explode( '.', $custom_domain );
+					$base         = $domain_parts[0];
+				} else {
+					// For subdirectory installs, use the path as the base
+					$base = trim( $custom_path, '/' );
+					// Use the last part of the path if there are multiple segments
+					$path_parts = explode( '/', $base );
+					$base       = end( $path_parts );
+					// If base is empty (root path), generate a random one
+					if ( empty( $base ) ) {
+						$base = 'site-' . wp_generate_password( 8, false );
+					}
+				}
+			} else {
+				$base = $assoc_args['slug'];
+			}
+		} else {
+			$base = $assoc_args['slug'];
+		}
 
 		/**
 		 * @var string $title
@@ -471,11 +536,25 @@ public function create( $args, $assoc_args ) {
 		}
 
 		if ( is_subdomain_install() ) {
-			$newdomain = $base . '.' . preg_replace( '|^www\.|', '', $current_site->domain );
-			$path      = $current_site->path;
+			if ( null !== $custom_domain ) {
+				// Use custom domain if provided via --url
+				$newdomain = $custom_domain;
+				$path      = $custom_path;
+			} else {
+				// Use default behavior
+				$newdomain = $base . '.' . preg_replace( '|^www\.|', '', $current_site->domain );
+				$path      = $current_site->path;
+			}
 		} else {
-			$newdomain = $current_site->domain;
-			$path      = $current_site->path . $base . '/';
+			if ( null !== $custom_domain ) {
+				// Use custom domain and path if provided via --url
+				$newdomain = $custom_domain;
+				$path      = $custom_path;
+			} else {
+				// Use default behavior
+				$newdomain = $current_site->domain;
+				$path      = $current_site->path . $base . '/';
+			}
 		}
 
 		$user_id = email_exists( $email );