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FastForward Defer

A minimal utility that brings defer-style execution (similar to Go) to PHP using object scope and destructors. It allows you to register callbacks that will run automatically at the end of a scope, in LIFO order (Last-In, First-Out).

Core Concept

A Defer instance represents a scope-bound execution stack.

• Register callbacks using $defer(...) or $defer->defer(...)
• Callbacks execute automatically when the object goes out of scope
• Execution is always LIFO (stack behavior)
• Execution is guaranteed during exception unwinding
• Errors inside callbacks are captured and reported, without interrupting the chain

Basic Usage

Output

Using Arguments

Deferred callbacks receive exactly the arguments you pass.

Output

⚠️ Execution Order Matters

Deferred callbacks execute in reverse order of registration.

Execution order:

Always register in reverse of the desired execution order.

Exception Safety

Deferred callbacks always run, even if an exception occurs.

Output

Nested Scopes

Each Defer instance is isolated.

Output

Helper Functions

defer()

Creates a new Defer instance.

scope()

Runs a block with an isolated defer scope.

using()

Structured resource management (acquire → use → cleanup).

Error Handling

Deferred callbacks never break execution flow.

• If a callback throws, execution continues
• Errors are forwarded to an ErrorReporter
• Default behavior uses error_log()

Custom Error Reporter

Composite Reporter

PSR Integration

PSR-3 Logger

PSR-14 Event Dispatcher

This allows multiple listeners (logging, metrics, tracing, etc.).

HTTP Middleware (PSR-15)

You can bind a Defer instance to a request lifecycle.

The middleware:

• creates a Defer per request
• injects it into request attributes
• ensures execution at the end of the request

Accessing Defer in Handlers

Execution Model

Within a single scope

• Last registered → runs first

Across nested scopes

• Inner scope resolves before outer

Design Principles

• Deterministic cleanup
• Minimal API
• No manual flush
• Failure isolation
• Extensible reporting

Notes

• Execution is triggered by __destruct()
• Do not share instances across scopes
• Prefer short-lived instances
• Avoid long-lived/global usage

When to Use

• resource cleanup
• file handling
• locks
• temporary state
• exception-safe teardown

When NOT to Use

• long-lived lifecycle management
• orchestration logic
• cases requiring explicit execution timing

Summary

Defer provides a strict and predictable cleanup model:

• automatic execution at scope end
• LIFO ordering
• safe failure handling
• pluggable reporting
• PSR-friendly integrations

It is intentionally small, deterministic, and constrained.

Contributing

See CONTRIBUTING.md for changelog fragments, local checks and the release-review flow.

Consumer agent skill

The package includes fast-forward-defer for application integration. It supports fast-forward/defer:^1.1; inspect the installed version. See skill installation and lifecycle for optional project synchronization with llm/skills ^1.15, guarded manual project/global copies and a pinned Skills CLI alternative. Shipping files does not install tooling or activate the skill in an agent session.