OutputCapture

Catches anything the application echoes outside the response body while a runtime with no SAPI output channel is handling the request.

Under a SAPI, echo from a template or a stray debug statement lands in the response and nobody notices. Under RoadRunner it lands on the process’s stdout, which is the relay RoadRunner speaks its protocol over, and under Swoole it goes to the server’s console. Both are worse than losing the output, so the loop wraps the pipeline in a buffer and applies a policy.

core.worker.stray_output: - append (default) fold it onto the response body, matching what a SAPI would have produced - discard drop it, with a log line naming the size - throw fail loudly, for development

Synopsis

final class OutputCapture

Source	Runtime/OutputCapture.php

Constants

Constant	Value	Description
POLICY_APPEND	'append'
POLICY_DISCARD	'discard'
POLICY_THROW	'throw'

Constructor

__construct()

public function __construct(?string $policy = null): mixed

Parameter	Type	Description
$policy	?``string

Returns mixed

Methods

Method	Description
apply(string $stray): string	Applies the configured policy, returning the text to append to the response body (” when there is nothing to append).
finish(): string	Unwinds every buffer opened since start() — application code may have opened its own and not closed it, e.g.
start(): void	Opens the capture buffer for one request.

apply()

public function apply(string $stray): string

Applies the configured policy, returning the text to append to the response body (” when there is nothing to append).

Parameter	Type	Description
$stray	string

Returns string

Throws	When
RuntimeException	when the policy is throw and output was captured.

finish()

public function finish(): string

Unwinds every buffer opened since start() — application code may have opened its own and not closed it, e.g.

a renderer that threw mid-render — and returns whatever was written, or ” when there was nothing.

ob_get_clean() pops the innermost buffer first, so the collected chunks come back inside-out and have to be reversed to reproduce write order.

Returns string

start()

public function start(): void

Opens the capture buffer for one request.

Records the buffer level beneath it and the level of its own buffer, which is what lets OutputCapture::finish() detect application code closing past it. Calling this while a capture is already open does nothing, so the nesting stays balanced.