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

When building tools that inspect PHP code, ReflectionGenerator::getTrace() helps answer a focused question: reports generator execution frames, including delegated yield from chains.

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

What Is ReflectionGenerator::getTrace()?

Reports generator execution frames, including delegated yield from chains.

Its method signature is:

public function getTrace(int $options = ...): array

Parameters:

• $options — Flags controlling the requested operation May be omitted.

Return value: array

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 = $generatorReflection->getTrace();
echo count($result) . " frame(s)";

Output:

1 frame(s)

Explanation: Reports generator execution frames, including delegated yield from chains.

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 = $generatorReflection->getTrace();
echo count($result) . " frame(s)";

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

Output:

1 frame(s)
Result type: array

Explanation: The trace changes with the generator's current suspension point.

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 = $generatorReflection->getTrace();
echo count($result) . " frame(s)";

// 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:

1 frame(s)
Entries: 1

Explanation: getExecutingLine reports one source location.

Important Behavior and Edge Cases

• The trace changes with the generator's current suspension point.
• getExecutingLine reports one source location.
• 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

• Reports generator execution frames, including delegated yield from chains.
• The trace changes with the generator's current suspension point.
• getExecutingLine reports one source location.

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