PHP ReflectionFiber::getCallable() Method: Usage and Examples

When building tools that inspect PHP code, ReflectionFiber::getCallable() helps answer a focused question: returns the callback with which the reflected fiber was created.

Reflection is useful in framework tooling, dependency injection, testing, code inspection and debugging.

What Is ReflectionFiber::getCallable()?

Returns the callback with which the reflected fiber was created.

Its method signature is:

public function getCallable(): callable

This method has no required arguments.

Return value: callable

Example 1: Inspect the basic behavior

Start with a self-contained PHP declaration and inspect the method result.

<?php

declare(strict_types=1);

$fiber = new Fiber(static function (): void {
    $count = 1;
    Fiber::suspend($count);
});
$fiber->start();
$fiberReflection = new ReflectionFiber($fiber);

$result = $fiberReflection->getCallable();
echo is_callable($result) ? "callable" : "not callable";

Output:

callable

Explanation: Returns the callback with which the reflected fiber was created.

Example 2: Compare a second case

Next, change the reflected declaration or parameter to observe a related situation.

<?php

declare(strict_types=1);

$fiber = new Fiber(static function (): void {
    $count = 2;
    Fiber::suspend($count);
});
$fiber->start();
$fiberReflection = new ReflectionFiber($fiber);

$result = $fiberReflection->getCallable();
echo is_callable($result) ? "callable" : "not callable";

// Check the returned value type before using the result.
echo "\nResult type: " . get_debug_type($result);

The exact output or reflected object details depend on the declaration and PHP runtime. Inspect the returned value before using it in application logic.

Explanation: Fiber reflection requires a started, suspended Fiber; a completed fiber has no executing frame.

Practical Example: Apply the operation in context

This final case shows how the same API can be used when inspecting application definitions.

<?php

declare(strict_types=1);

$fiber = new Fiber(static function (): void {
    $count = 3;
    Fiber::suspend($count);
});
$fiber->start();
$fiberReflection = new ReflectionFiber($fiber);

$result = $fiberReflection->getCallable();
echo is_callable($result) ? "callable" : "not callable";

// Use the reflection result in a simple decision.
if (is_bool($result)) {
    echo "\nStatus: " . ($result ? "yes" : "no");
} elseif (is_array($result)) {
    echo "\nEntries: " . count($result);
} elseif ($result === null) {
    echo "\nNo value returned";
} else {
    echo "\nReflection result available";
}

Output:

callable
Reflection result available

Explanation: getFiber returns the original Fiber object.

Important Behavior and Edge Cases

• Fiber reflection requires a started, suspended Fiber; a completed fiber has no executing frame.
• getFiber returns the original Fiber object.
• Reflection describes declarations and runtime state; requesting metadata does not automatically validate or sanitize application input.

Comparison With Related Approaches

Common Beginner Mistakes

Key Takeaways

• Returns the callback with which the reflected fiber was created.
• Fiber reflection requires a started, suspended Fiber; a completed fiber has no executing frame.
• getFiber returns the original Fiber object.

Use ReflectionFiber::getCallable() when you need the precise metadata or behavior demonstrated above. Keep the target declaration and relevant PHP version in mind when adapting the examples.