MU Cookie Debugger

cookie-logger.php

<?php
/**
 * Plugin Name: MU Cookie Debugger
 * Description: Logs WordPress login cookie diagnostics for troubleshooting cookie issues.
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

if ( ! function_exists( 'mcd_log' ) ) {
	function mcd_log( string $label, array $context = [] ): void {
		$log_file = WP_CONTENT_DIR . '/mu-cookie-debug.log';

		$line = '[' . gmdate( 'Y-m-d H:i:s' ) . ' UTC] ' . $label;

		if ( ! empty( $context ) ) {
			$line .= ' ' . wp_json_encode(
				$context,
				JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE
			);
		}

		$line .= PHP_EOL;

		error_log( $line, 3, $log_file );
	}
}

if ( ! function_exists( 'mcd_set_cookie_names' ) ) {
	function mcd_set_cookie_names(): array {
		$names = [];

		foreach ( headers_list() as $header ) {
			if ( stripos( $header, 'Set-Cookie:' ) === 0 ) {
				$cookie = trim( substr( $header, strlen( 'Set-Cookie:' ) ) );
				$pair   = explode( ';', $cookie, 2 )[0];
				[$name] = array_pad( explode( '=', $pair, 2 ), 2, '' );

				$names[] = trim( $name );
			}
		}

		return array_values( array_unique( $names ) );
	}
}

if ( ! function_exists( 'mcd_snapshot' ) ) {
	function mcd_snapshot( string $stage ): void {
		$test_cookie = defined( 'TEST_COOKIE' ) ? TEST_COOKIE : 'wordpress_test_cookie';

		$headers_sent = headers_sent( $file, $line );

		$context = [
			'stage'   => $stage,
			'request' => [
				'method'     => $_SERVER['REQUEST_METHOD'] ?? null,
				'host'       => $_SERVER['HTTP_HOST'] ?? null,
				'uri'        => $_SERVER['REQUEST_URI'] ?? null,
				'referer'    => $_SERVER['HTTP_REFERER'] ?? null,
				'user_agent' => $_SERVER['HTTP_USER_AGENT'] ?? null,
				'https'      => $_SERVER['HTTPS'] ?? null,
			],
			'wordpress' => [
				'is_ssl'   => function_exists( 'is_ssl' ) ? is_ssl() : null,
				'home_url' => function_exists( 'home_url' ) ? home_url( '/' ) : null,
				'site_url' => function_exists( 'site_url' ) ? site_url( '/' ) : null,
			],
			'cookies' => [
				'expected_test_cookie'   => $test_cookie,
				'has_expected_test_cookie'=> isset( $_COOKIE[ $test_cookie ] ),
				'cookie_names'           => array_keys( $_COOKIE ),
				'http_cookie_header'     => $_SERVER['HTTP_COOKIE'] ?? null,
			],
			'headers' => [
				'headers_sent'    => $headers_sent ? ( $file . ':' . $line ) : false,
				'set_cookie_names' => mcd_set_cookie_names(),
			],
			'constants' => [
				'COOKIE_DOMAIN'      => defined( 'COOKIE_DOMAIN' ) ? COOKIE_DOMAIN : null,
				'COOKIEPATH'         => defined( 'COOKIEPATH' ) ? COOKIEPATH : null,
				'SITECOOKIEPATH'     => defined( 'SITECOOKIEPATH' ) ? SITECOOKIEPATH : null,
				'ADMIN_COOKIE_PATH'  => defined( 'ADMIN_COOKIE_PATH' ) ? ADMIN_COOKIE_PATH : null,
				'TEST_COOKIE'        => defined( 'TEST_COOKIE' ) ? TEST_COOKIE : null,
				'LOGGED_IN_COOKIE'   => defined( 'LOGGED_IN_COOKIE' ) ? LOGGED_IN_COOKIE : null,
				'AUTH_COOKIE'        => defined( 'AUTH_COOKIE' ) ? AUTH_COOKIE : null,
				'SECURE_AUTH_COOKIE' => defined( 'SECURE_AUTH_COOKIE' ) ? SECURE_AUTH_COOKIE : null,
			],
		];

		mcd_log( 'cookie snapshot', $context );
	}
}

$GLOBALS['mcd_login_request'] = false;

add_action( 'login_init', function () {
	$GLOBALS['mcd_login_request'] = true;
	mcd_snapshot( 'login_init' );
}, 1 );

add_action( 'wp_login_failed', function ( $username ) {
	$GLOBALS['mcd_login_request'] = true;
	mcd_snapshot( 'wp_login_failed: ' . $username );
}, 10, 1 );

add_action( 'login_footer', function () {
	if ( ! empty( $GLOBALS['mcd_login_request'] ) ) {
		mcd_snapshot( 'login_footer' );
	}
}, 999 );

add_action( 'shutdown', function () {
	if ( ! empty( $GLOBALS['mcd_login_request'] ) ) {
		mcd_snapshot( 'shutdown' );
	}
}, 999 );