formstream.php

См. документацию.

<?php
 
namespace Bitrix\Main\Web\Http;
 
class FormStream extends Stream
{
    public function __construct(array $data)
    {
        parent::__construct('php://temp', 'r+');
 
        $this->build($data);
        $this->rewind();
    }
 
    protected function build(array $data)
    {
        $this->write(http_build_query($data, '', '&'));
    }
}