Provide debug information for a WordPress installation using FishPig. Especially useful for Multisite/Network installs.

wp-debug.php

<?php
/**
 * @FishPig.com
 */
ini_set('display_errors', 1);
error_reporting(E_ALL);

$isCli = PHP_SAPI === 'cli';

define('DS', DIRECTORY_SEPARATOR);

try {
    // Load WordPress code
    _bootstrap_wordpress();

    // Extract data we need for debugging
    $data = [
        // Get wp-config.php
        // Remove DB_PASSWORD for security
        'wp-config.php' => _get_wp_config_file(),
        '.htaccess' => _get_htaccess_file(),
        'data' => _get_data_from_database()
    ];

    if (!$isCli) {
        // If a browser, let's send a header
        header('Content-Type: application/json;charset=utf-8');
    }

    echo json_encode($data);
} catch (\Exception $e) {
    if ($isCli) {
        echo $e->getMessage() . "\n\n" . $e->getTraceAsString() . "\n\n";
        exit(1);
    } else {
        echo sprintf(
            '<h1><span style="color:red;">Exception:</span> %s</h1><pre>%s</pre>',
            $e->getMessage(),
            $e->getTraceAsString()
        );
    }
}

/**
 *
 */
function _bootstrap_wordpress(): void
{
    $wpLoadFile = __DIR__ . DS . 'wp-load.php';

    if (!is_file($wpLoadFile)) {
        throw new \RuntimeException(
            sprintf(
                'Cannot find WordPress. Failed @ "%s"',
                $wpLoadFile
            )
        );
    }

    require_once $wpLoadFile;

    if (!defined('ABSPATH')) {
        throw new \RuntimeException(
            'Unable to find ABSPATH. WordPress bootstrap failed'
        );
    }
}

/**
 * Try to get wp-config.phpfile
 * If fails, return error message
 * All data will be returned as a JSON string
 * The password for the DB will be removed for security
 */
function _get_wp_config_file(): string
{
    return _read_file(
        ABSPATH . 'wp-config.php',
        function ($data) {
            // Remove Database password
            return preg_replace(
                '/(define\(\s*([\'"]{1})DB_PASSWORD\2\s*,\s*([\'"]{1}))[^\3]+(\3\s*\))/U',
                '$1--REMOVED--$4',
                $data
            );
        }
    );
}

/**
 * Get .htaccess file
 */
function _get_htaccess_file()
{
    return _read_file(ABSPATH . '.htaccess');
}

/**
 * Reads $file and handles errors
 */
function _read_file($file, \Closure $callback = null): string
{
    if (!file_exists($file)) {
        return [
            'error' => sprintf('File does not exist @ "%s"', $file),
            'source' => 'file_exists'
        ];
    } elseif (!is_readable($file)) {
        return [
            'error' => sprintf('File is not readable @ "%s"', $file),
            'source' => 'is_readable'
        ];
    }

    // Try to catch any errors
    ob_start();
    $data = @file_get_contents($file);
    if ($output = ob_get_clean()) {
        return [
            'error' => (string)$output,
            'source' => 'file_get_contents'
        ];
    }

    return is_callable($callback) ? $callback($data) : $data;
}

/**
 *
 */
function _get_data_from_database(): array
{
    global $wpdb;
    $data = [
        'is_multisite' => (int)is_multisite(),
        'blogs' => []
    ];
    $wpdb->show_errors = false;

    try {
        $blogs = $wpdb->get_results( "SELECT blog_id, domain, path FROM {$wpdb->prefix}blogs WHERE deleted = 0", ARRAY_A );
    } catch (\Exception $e) {
        // Multisite not enabled in the DB
    }

    if (!isset($blogs) || !$blogs || (is_array($blogs) && count($blogs) === 0)) {
        $blogs = [['blog_id' => 1]];
    }

    $urlFuncMap = [
        'home' => 'get_home_url',
        'siteurl' => 'get_site_url'
    ];

    foreach ($blogs as $blog) {
        $blogId = (int)$blog['blog_id'];
        $key = 'blog_' . $blogId;
        $prefix = $blogId === 1 ? $wpdb->prefix : $wpdb->prefix . $blogId . '_';
        $data['blogs'][$key] = $blog;
        // Get URLs via functions
        // This gives plugins a chance to change values
        foreach ($urlFuncMap as $optionName => $func) {
            $data['blogs'][$key][$optionName] = _try_catch_callback(function() use($func) { return $func(); });
            $data['blogs'][$key]['option__' . $optionName] = _try_catch_callback(function() use ($wpdb, $prefix, $optionName) {
                return $wpdb->get_var("SELECT option_value FROM {$prefix}options WHERE option_name = '{$optionName}' LIMIT 1");
            });
        }
    }

    return $data;
}

/**
 *
 */
function _try_catch_callback(\Closure $callback)
{
    try {
        return $callback();
    } catch (\Exception $e) {
        return $e->getMessage();
    }
}