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

When building tools that inspect PHP code, ReflectionFiber::getExecutingLine() helps answer a focused question: returns the source-code line where the fiber is suspended.

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

What Is ReflectionFiber::getExecutingLine()?

Returns the source-code line where the fiber is suspended.

Its method signature is:

public function getExecutingLine(): ?int

This method has no required arguments.

Return value: ?int

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 = $fiberReflection->getExecutingLine();
var_dump($result);

Output:

int(7)

Explanation: Returns the source-code line where the fiber is suspended.

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 = $fiberReflection->getExecutingLine();
var_dump($result);

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

Output:

int(7)

Result type: int

Explanation: Line numbers depend on the actual source file, so do not hard-code them.

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 = $fiberReflection->getExecutingLine();
var_dump($result);

// 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:

int(7)

Reflection result available

Explanation: getTrace returns a stack trace with more context.

Important Behavior and Edge Cases

• Line numbers depend on the actual source file, so do not hard-code them.
• getTrace returns a stack trace with more context.
• 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 source-code line where the fiber is suspended.
• Line numbers depend on the actual source file, so do not hard-code them.
• getTrace returns a stack trace with more context.

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