Callback Describer

CallbackDescriber converts a PHP callable into a human-readable string. Built-in reporters use it so logs and events can tell you which deferred callback failed.

Why it exists

Without a helper like this, generic error reporters would only know that "some callable" failed. CallbackDescriber adds context such as:

the function name
the class and method
the closure source file and line
whether the callback was an invokable object

Supported callable shapes

String function names such as 'strlen'
Array callables such as [SomeClass::class, 'handle']
Closures
First-class callables, which are represented as closures
Invokable objects

use FastForward\Defer\Support\CallbackDescriber;

final class ExampleInvoker
{
    public static function staticHandle(): void {}

    public function handle(): void {}

    public function __invoke(): void {}
}

$object = new ExampleInvoker();

$callbacks = [
    'strlen',
    [ExampleInvoker::class, 'staticHandle'],
    [$object, 'handle'],
    static fn(): null => null,
    ExampleInvoker::staticHandle(...),
    $object,
];

foreach ($callbacks as $callback) {
    echo CallbackDescriber::describe($callback) . "\n";
}

What to expect from the output

String functions stay unchanged.
Array callables become Class::method or Class->method .
Closures become Closure@/path/to/file.php:line .
Invokable objects become Class::__invoke .

One subtle but important detail: first-class callables created with ... are closures, so they are described as closures, not as Class::method . If you want method-style output, pass an array callable instead.

Where it is used

ErrorLogErrorReporter
PsrLoggerErrorReporter
PsrEventDispatcherErrorReporter

See Support Utilities for the compact API reference.