Fix incorrect home/siteurl when WP-CLI runs from root filesystem

features/core-install.feature

@@ -177,6 +177,87 @@ Feature: Install WordPress core
       """
     And the return code should be 0
 
+  Scenario: Verify correct siteurl and home when URL has no path
+    Given an empty directory
+    And WP files
+    And wp-config.php
+    And a database
+
+    When I run `wp core install --url=example.com --title=Test --admin_user=wpcli --admin_email=wpcli@example.org --admin_password=password --skip-email`
+    Then STDOUT should contain:
+      """
+      Success: WordPress installed successfully.
+      """
+
+    When I run `wp option get home`
+    Then STDOUT should be:
+      """
+      http://example.com
+      """
+
+    When I run `wp option get siteurl`
+    Then STDOUT should be:
+      """
+      http://example.com
+      """
+
+  Scenario: Verify correct siteurl and home when URL has a path
+    Given an empty directory
+    And WP files
+    And wp-config.php
+    And a database
+
+    When I run `wp core install --url=example.com/subdir --title=Test --admin_user=wpcli --admin_email=wpcli@example.org --admin_password=password --skip-email`
+    Then STDOUT should contain:
+      """
+      Success: WordPress installed successfully.
+      """
+
+    When I run `wp option get home`
+    Then STDOUT should be:
+      """
+      http://example.com/subdir
+      """
+
+    When I run `wp option get siteurl`
+    Then STDOUT should be:
+      """
+      http://example.com/subdir
+      """
+
+  Scenario: Install with simulated root filesystem WP-CLI executable location
+    Given an empty directory
+    And WP files
+    And wp-config.php
+    And a database
+    And a problematic-server-vars.php file:
+      """
+      <?php
+      // Simulate WP-CLI being executed from root filesystem (e.g., /wp)
+      // This is the problematic scenario that the fix addresses
+      $_SERVER['PHP_SELF'] = '/wp';
+      $_SERVER['SCRIPT_NAME'] = '/wp';
+      $_SERVER['SCRIPT_FILENAME'] = '/wp';
+      """
+
+    When I run `wp core install --url=https://example.com --title=Test --admin_user=wpcli --admin_email=wpcli@example.org --admin_password=password --skip-email --require=problematic-server-vars.php`
+    Then STDOUT should contain:
+      """
+      Success: WordPress installed successfully.
+      """
+
+    When I run `wp option get home`
+    Then STDOUT should be:
+      """
+      https://example.com
+      """
+
+    When I run `wp option get siteurl`
+    Then STDOUT should be:
+      """
+      https://example.com
+      """
+
   @less-than-php-7
   Scenario: Install WordPress with locale set to de_DE on WP < 4.0
     Given an empty directory

src/Core_Command.php

@@ -691,6 +691,35 @@ function wp_new_blog_notification() {
 		// which is normally a runtime argument
 		if ( isset( $assoc_args['url'] ) ) {
 			WP_CLI::set_url( $assoc_args['url'] );
+
+			// Fix $_SERVER['PHP_SELF'] and $_SERVER['SCRIPT_NAME'] to prevent incorrect
+			// URL detection by WordPress during installation. When WP-CLI is executed from
+			// the root of the filesystem (e.g., /wp), these variables contain the WP-CLI
+			// executable path rather than the WordPress installation path, which causes
+			// wp_guess_url() to construct incorrect URLs.
+			$url_parts = Utils\parse_url( $assoc_args['url'] );
+			$path      = isset( $url_parts['path'] ) ? $url_parts['path'] : '/';
+
+			// Ensure path represents a PHP script for proper WordPress URL detection.
+			// If the path doesn't already end with a file (no extension in basename),
+			// append '/index.php' to represent the WordPress entry point.
+			$path = rtrim( $path, '/' );
+			if ( empty( $path ) ) {
+				$path = '/index.php';
+			} elseif ( '' === pathinfo( $path, PATHINFO_EXTENSION ) ) {
+				// Path doesn't end with a file, append /index.php
+				$path .= '/index.php';
+			}
+
+			$_SERVER['PHP_SELF']    = $path;
+			$_SERVER['SCRIPT_NAME'] = $path;
+
+			// Set SCRIPT_FILENAME to the actual WordPress index.php if available.
+			// This is optional and only set when ABSPATH is defined and index.php exists.
+			// If not set, WordPress can still function using PHP_SELF and SCRIPT_NAME.
+			if ( file_exists( Utils\trailingslashit( ABSPATH ) . 'index.php' ) ) {
+				$_SERVER['SCRIPT_FILENAME'] = Utils\trailingslashit( ABSPATH ) . 'index.php';
+			}
 		}
 
 		$public   = true;