symfony/process · error · BadMethodCallException

Cannot serialize Symfony\Component\Process\Pipes\UnixPipes

Error message

Cannot serialize Symfony\Component\Process\Pipes\UnixPipes

What it means

UnixPipes holds open OS file descriptors for process I/O, which cannot be meaningfully captured by PHP serialization. Attempting to serialize() a UnixPipes instance triggers __serialize(), which deliberately throws BadMethodCallException.

Solutions

1. Do not serialize objects holding live pipes; finish or close the process first
2. Store only serializable state (commandline, cwd, env) and recreate the Process later via new Process(...)
3. Exclude the pipes/Process property from serialization using __sleep()/__serialize() on the enclosing class

Example fix

// before
$cache->set('job', $process); // contains live pipes
// after
$cache->set('job', ['command' => $process->getCommandLine(), 'cwd' => $process->getWorkingDirectory()]);

if ($process->isRunning()) { throw new \LogicException('Cannot persist a running process'); }

function isSerializable(mixed $v): bool { try { serialize($v); return true; } catch (\Throwable) { return false; } }

try { $data = serialize($obj); } catch (\BadMethodCallException $e) { $data = serialize($obj->toDescriptor()); }

When it happens

Trigger: serialize($process->getProcessPipes()), serializing an object graph that contains live UnixPipes (e.g. serializing a running Process or storing it in a serializable cache/session).

Common situations: Putting a live Process into a session, cache, or queue payload while it is running; var_export/serialize debugging of a running process.

Understand the failure class

Background: "JSON serialization failed", "not JSON serializable", "Failed to serialize": why JSON marshaling errors happen and how to fix them — this error's family across 46 libraries.

Related errors

• Cannot unserialize Symfony\Component\Process\Pipes\UnixPipes
• Cannot serialize…
• Cannot serialize Symfony\Component\Process\Process
• Cannot unserialize…
• Cannot unserialize Symfony\Component\Process\Process

AI-assisted analysis of symfony/process@99b85026db (2026-09-14). Data as JSON: /api/errors/0e761a822c1aa9f6. Report an issue: GitHub.

Appendix: source

Thrown at Pipes/UnixPipes.php:36

 *
 * @author Romain Neutron <imprec@gmail.com>
 *
 * @internal
 */
class UnixPipes extends AbstractPipes
{
    public function __construct(
        private ?bool $ttyMode,
        private bool $ptyMode,
        mixed $input,
        private bool $haveReadSupport,
    ) {
        parent::__construct($input);
    }

    public function __serialize(): array
    {
        throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
    }

    public function __unserialize(array $data): void
    {
        throw new \BadMethodCallException('Cannot unserialize '.__CLASS__);
    }

    public function __destruct()
    {
        $this->close();
    }

    public function getDescriptors(): array
    {
        if (!$this->haveReadSupport) {
            $nullstream = fopen('/dev/null', 'c');

            return [

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