fix: Add multipart form-data support for Laravel HTTP server

[homiedopie]

Problem

• Multipart form-data requests were not fully parsed in the Laravel HTTP server driver.
• As a result, uploaded files and nested multipart fields were not reliably available in the Laravel Request object.

Fix

• Added multipart parsing support using Amp form parser and mapped payloads to Symfony/Laravel-compatible request structures.
• Implemented normalization for nested fields and uploaded files, and converted uploaded parts into Laravel UploadedFile instances.

Test

• URL-encoded form body
• Multipart form with file uploads (from: @gtg-bantonio)
• Multipart form with nested fields (from: @gtg-bantonio)

Verification

• Verified my SPA test cases using form-data

Note

• With the help of Github Copilot (GPT 5.3 Codex)

Related

Related #177 - Thanks to @gtg-bantonio
Fixes #1495

[gtg-bantonio]

Good day, I detect an error when you don't select a file: The browser send a file with the header filename empty, and in the parser it should return a file with the UPLOAD_ERR_NO_FILE flag set, not return a default value.

https://github.com/pestphp/pest-plugin-browser/pull/200/changes#diff-b56f173c966197dc61e8e52e50e147d3ed935d600b16d78bc2507808a9a441f7R538-R542

Additionally, I notice that other corner cases like when the file is greater that the max file size defined in the INI file (UPLOAD_ERR_INI_SIZE and UPLOAD_ERR_FORM_SIZE)

[homiedopie]

@gtg-bantonio Thanks for the feedback. Ill check it out and will add some test as well!

[homiedopie]

@gtg-bantonio I addressed it on the new fixes I have added. Can you please check on your end? Thank you!

[gtg-bantonio]

I found another bug, with nested indexed fields in a linear sequence:
Let's assume the browser send the following multipart data (in URL-encoded notation to don't make it too long)

extra = 'Test'
data[0][field1] = 1
data[0][field2] = 1
data[1][field1] = 2
data[1][field2] = 0

The decoded data should be (in PHP array notation)

[
  'extra' => 'Test',
  'data' => [
    0 => [
      'field1' => '1',
      'field2' => '1',
    ],
    1 => [
      'field1' => '2',
      'field2' => '0',
    ],
  ],
]

But instead the parser returns:

[
  'extra' => 'Test',
  'data' => [
    0 => [
      'field1' => '1',
      'field2' => ['0', '1'],
    ],
    1 => [
      'field1' => '2',
      'field2' => '0',
    ],
  ],
]

[akulmehta]

Can I ask, how is this PR different from the other PR #177 ? Confused on which one to follow.

[gtg-bantonio]

@akulmehta in this PR, the library that use is the amphp/http-server-form-parser with some manipulation to respect the PHP $_POST structure, an in my PR #177 I extract the ReactPHP MultipartParser that parse directly to the correct structure, but with some maintenance burden

[homiedopie]

@gtg-bantonio - thanks for explaining it! I addressed the issue already and separated the test (dedicated to multipart upload/parameters)

[gtg-bantonio]

I can't found another error with our full script, and the tests and code are better that mine, so I will close my PR in favor of yours

[homiedopie]

@gtg-bantonio - Thanks again for your help! wouldnt be possible without your guidance and inputs!