Troubleshooting JSON Response with Acorn (Sage 10) Laravel Routing in WordPress and Header Modification Warning

sage
,
1

I want to use REST API functionality to return JSON data. There are two methods I know of:

  1. WordPress native REST API implementation: Use WordPress hooks (add_action) to register a custom REST API route (register_rest_route).
  2. Sage 10 theme, based on Laravel: Use Laravel routes, requiring ACORN_ENABLE_EXPIRIMENTAL_ROUTER='True' in the .env file.

When testing the Laravel routing method, with the following code:

routes/api.php:

Route::get('test/data', function () {
    return response()->json(['message' => 'Hello, World!']);
});

.htaccess:

<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule . /index.php [L]
</IfModule>

Accessing http://localhost/api/test/data returns:

{"message":"Hello, World!"}<!doctype html>
<html lang="zh-CN">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Page Not Found &#8211; Glamoré &#8211; Second-hand luxury vintage bags</title>
    <meta name='robots' content='noindex, nofollow' />
    ...
    ...

Accessing http://localhost/index.php/api/test/data returns:

{"message":"Hello, World!"}

However, there’s a warning in php_error.log:

[Sat Nov 25 01:10:57 2023] PHP Warning:  Cannot modify header information - headers already sent by (output started at /Users/wangkairen/Sites/localhost/wp-glamore/wp-content/themes/kieran-craft/vendor/symfony/http-foundation/Response.php:1325) in /Users/wangkairen/Sites/localhost/wp-glamore/wp-includes/pluggable.php on line 1435
[Sat Nov 25 01:10:57 2023] PHP Warning:  Cannot modify header information - headers already sent by (output started at /Users/wangkairen/Sites/localhost/wp-glamore/wp-content/themes/kieran-craft/vendor/symfony/http-foundation/Response.php:1325) in /Users/wangkairen/Sites/localhost/wp-glamore/wp-includes/pluggable.php on line 1438

The desired outcome is to have http://localhost/index.php/api/test/data return {“message”:“Hello, World!”}, without PHP header modification warnings. Is this issue related to Acorn’s illuminate/routing limitations? Should I stick to the native WordPress REST API for achieving the desired JSON response?

I’m using WordPress + Sage 10 (v10.7.0) with MAMP PRO, and I encounter the mentioned issue with PHP versions 8.0.2 to 8.2.0.

2

From what I read about this issue (Header modified at wp-includes/pluggable.php on line 1435), it has something to do with PHP Notices/Warnings. Somewhere else a PHP Notice/Warning is emitted, which causes PHP to send the HTTP headers too early. You can disable the causative PHP Notice/Warnings by setting WP_DEBUG constant to false. However, there may be an underlying issue, as the reason for the PHP Notice/Warning, so you may want to fix the underlying issue rather than suppressing it.