"Cannot modify header information" error encountered while streaming #9357
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Livewire versionv3.6.3 Laravel versionv12.16.0 Which PHP version are you using?PHP 8.2 What is the problem?I'm trying to use Livewire streams in my Laravel app but I keep getting the following error from the Laravel logs, and also, on the front end, I'm getting a 
At first I thought it was a Livewire bug, but after checking I found that Livewire streaming worked fine in Laravel framework v10.48.29 without triggering any errors. However, Livewire streaming have issue in both v11.0.0 and the latest v12.16.0. And I installed Livewire with the same version between v10 and v12. By the way, I'm using Herd. Code snippetsThe codes is CountDown component that copied from https://livewire.laravel.com/docs/wire-stream. <?php
namespace App\Livewire;
use Livewire\Component;
class CountDown extends Component
{
public $start = 3;
public function begin()
{
while ($this->start >= 0) {
// Stream the current count to the browser...
$this->stream(
to: 'count',
content: $this->start,
replace: true,
);
// Pause for 1 second between numbers...
sleep(1);
// Decrement the counter...
$this->start = $this->start - 1;
};
}
public function render()
{
return view('livewire.count-down');
}
}<div>
<button wire:click="begin">Start count-down</button>
<h1>Count: <span wire:stream="count">{{ $start }}</span></h1>
</div>Unfortunately, wirebox is using Laravel 10 version which streaming is works fine. You could check out my repo below. I installed a fresh new Laravel app with just Livewire installed to make sure nothing else was affecting the test results.
laravel/laravel => v10.3.3 laravel/laravel => v11.6.1 laravel/laravel => v12.0.9 Wirebox URLHow do you expect it to work?This should not give any errors, as streaming worked fine in Laravel v10. Please confirm (incomplete submissions will not be addressed)
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Replies: 4 comments 4 replies
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After digging deeper into the code, I found this PR symfony/symfony#60377 that triggered above issue. |
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Took me 10 hours to find... {
"require": {
...
"symfony/http-foundation": "~7.2.0"
...
}
} |
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@sarukomine, @david371571 - just ran into this as well. Thanks for the work in diagnosing this! |
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According to symphony this should be fixed in Livewire symfony/symfony#60603 @joshhanley I think it's worth having a look if possible. |
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@MrCrayon I personally think they should fix it as they have introduced a breaking change in a minor release. At the moment I don't have time to look at it. But PRs to fix it on the Livewire end (if that's actually required) would be welcome! 🙂 |
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@joshhanley I think that in an ideal world Livewire should be fixed because sending headers after content raises a PHP Warning, that warning was previously suppressed by Symphony but it's still something that should not happen. In this case the problems raised by this fix in Symphony in my opinion outweights the benefits, even I completely understand this is a free opensource library and I would do my best to contribute but I have to admit my knowledge of this codebase is close to zero 😁 I managed to make livewire stream work with this quite rudimental fix here $response = $finish($responsePayload);
/**
* Headers have already been sent by stream
* we need to send the output without additional headers
**/
if (headers_sent()) {
echo json_encode($response);
exit(0);
}
return $response;
}I am not sure if there is a better place or way to do it. |
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That naive solution, even if working, was clearly going to break Laravel pipeline. |
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Another workaround is to suppress the error so that packages can be up to date. Add in public function boot(): void
{
set_error_handler(function ($errno, $errstr, $errfile) {
if (str_contains($errstr, 'Cannot modify header information - headers already sent') &&
(str_contains($errfile, 'livewire/src/Features/SupportStreaming/SupportStreaming.php'))) {
return true;
}
return false;
}, E_ERROR);
} |
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After digging deeper into the code, I found this PR symfony/symfony#60377 that triggered above issue.