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

When building tools that inspect PHP code, ReflectionGenerator::isClosed() helps answer a focused question: tests whether the generator has finished executing or been closed.

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

What Is ReflectionGenerator::isClosed()?

Tests whether the generator has finished executing or been closed.

Its method signature is:

public function isClosed(): bool

This method has no required arguments.

Return value: bool

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 = $generatorReflection->isClosed();
var_dump($result);

Output:

bool(false)

Explanation: Tests whether the generator has finished executing or been closed.

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 = $generatorReflection->isClosed();
var_dump($result);

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

Output:

bool(false)

Result type: bool

Explanation: A generator that has never advanced is not closed simply because it has no visible output.

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 = $generatorReflection->isClosed();
var_dump($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:

bool(false)

Status: no

Explanation: Generator::valid checks whether iteration can currently continue.

Important Behavior and Edge Cases

• A generator that has never advanced is not closed simply because it has no visible output.
• Generator::valid checks whether iteration can currently continue.
• 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

• Tests whether the generator has finished executing or been closed.
• A generator that has never advanced is not closed simply because it has no visible output.
• Generator::valid checks whether iteration can currently continue.

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