PHP ReflectionGenerator::getExecutingGenerator() Method: Usage and Examples

When building tools that inspect PHP code, ReflectionGenerator::getExecutingGenerator() helps answer a focused question: returns the innermost currently active Generator for a delegating generator.

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

What Is ReflectionGenerator::getExecutingGenerator()?

Returns the innermost currently active Generator for a delegating generator.

Its method signature is:

public function getExecutingGenerator(): Generator

This method has no required arguments.

Return value: Generator

Example 1: Inspect the basic behavior

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

<?php

declare(strict_types=1);

function makeSequence(): Generator {
    yield "first" => 10;
    yield from ["next" => 20];
}
$generator = makeSequence();
$generator->rewind();
$generatorReflection = new ReflectionGenerator($generator);

$result = $generatorReflection->getExecutingGenerator();
echo $result instanceof Generator ? "active generator" : "other";

Output:

active generator

Explanation: Returns the innermost currently active Generator for a delegating generator.

Example 2: Compare a second case

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

<?php

declare(strict_types=1);

function makeSequence(): Generator {
    yield "first" => 11;
    yield from ["next" => 21];
}
$generator = makeSequence();
$generator->rewind();
$generatorReflection = new ReflectionGenerator($generator);

$result = $generatorReflection->getExecutingGenerator();
echo $result instanceof Generator ? "active generator" : "other";

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

Output:

active generator
Result type: Generator

Explanation: With yield from the active generator can differ from the original object.

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);

function makeSequence(): Generator {
    yield "first" => 12;
    yield from ["next" => 22];
}
$generator = makeSequence();
$generator->rewind();
$generatorReflection = new ReflectionGenerator($generator);

$result = $generatorReflection->getExecutingGenerator();
echo $result instanceof Generator ? "active generator" : "other";

// 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:

active generator
Reflection result available

Explanation: getFunction returns reflection for the generator function.

Important Behavior and Edge Cases

• With yield from the active generator can differ from the original object.
• getFunction returns reflection for the generator function.
• 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 innermost currently active Generator for a delegating generator.
• With yield from the active generator can differ from the original object.
• getFunction returns reflection for the generator function.

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