Seldaek/monolog · error · InvalidArgumentException

A stream must either be a resource or a string.

Error message

A stream must either be a resource or a string.

What it means

Error "A stream must either be a resource or a string." thrown in Seldaek/monolog.

Source

Thrown at src/Monolog/Handler/StreamHandler.php:75

                // use max 10% of allowed memory for the chunk size, and at least 100KB
                $this->streamChunkSize = min(static::MAX_CHUNK_SIZE, max((int) ($phpMemoryLimit / 10), 100 * 1024));
            } else {
                // memory is unlimited, set to the default 10MB
                $this->streamChunkSize = static::DEFAULT_CHUNK_SIZE;
            }
        } else {
            // no memory limit information, set to the default 10MB
            $this->streamChunkSize = static::DEFAULT_CHUNK_SIZE;
        }

        if (\is_resource($stream)) {
            $this->stream = $stream;

            stream_set_chunk_size($this->stream, $this->streamChunkSize);
        } elseif (\is_string($stream)) {
            $this->url = Utils::canonicalizePath($stream);
        } else {
            throw new \InvalidArgumentException('A stream must either be a resource or a string.');
        }

        $this->fileOpenMode = $fileOpenMode;
        $this->filePermission = $filePermission;
        $this->useLocking = $useLocking;
    }

    /**
     * @inheritDoc
     */
    public function reset(): void
    {
        parent::reset();

        // auto-close on reset to make sure we periodically close the file in long running processes
        // as long as they correctly call reset() between jobs
        if ($this->url !== null && $this->url !== 'php://memory') {
            $this->close();

View on GitHub (pinned to 57eb102834)

When it happens

Trigger: Thrown at src/Monolog/Handler/StreamHandler.php:75 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Seldaek/monolog@57eb102834 (2026-08-17). Data as JSON: /api/errors/f8ad4789c0ad4c5f. Report an issue: GitHub.