PHP ReflectionUnionType::getTypes() Method: Usage and Examples

When building tools that inspect PHP code, ReflectionUnionType::getTypes() helps answer a focused question: returns the constituent types of a union declaration such as int|string.

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

What Is ReflectionUnionType::getTypes()?

Returns the constituent types of a union declaration such as int|string.

Its method signature is:

public function getTypes(): array

This method has no required arguments.

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 inspectValue(int|string $value): void {}
$typeReflection = (new ReflectionFunction("inspectValue"))->getParameters()[0]->getType();

$result = $typeReflection->getTypes();
echo implode(" | ", array_map(static fn($type) => $type->getName(), $result));

Output:

string | int

Explanation: Returns the constituent types of a union declaration such as int|string.

Example 2: Compare a second case

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

<?php

declare(strict_types=1);

function inspectValue(float|bool $value): void {}
$typeReflection = (new ReflectionFunction("inspectValue"))->getParameters()[0]->getType();

$result = $typeReflection->getTypes();
echo implode(" | ", array_map(static fn($type) => $type->getName(), $result));

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

Output:

float | bool
Result type: array

Explanation: A union accepts any member type; an intersection requires all members.

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 inspectValue(DateTime|DateTimeImmutable $value): void {}
$typeReflection = (new ReflectionFunction("inspectValue"))->getParameters()[0]->getType();

$result = $typeReflection->getTypes();
echo implode(" | ", array_map(static fn($type) => $type->getName(), $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:

DateTime | DateTimeImmutable
Entries: 2

Explanation: ReflectionIntersectionType::getTypes reads intersection members.

Important Behavior and Edge Cases

• A union accepts any member type; an intersection requires all members.
• ReflectionIntersectionType::getTypes reads intersection members.
• 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 constituent types of a union declaration such as int|string.
• A union accepts any member type; an intersection requires all members.
• ReflectionIntersectionType::getTypes reads intersection members.

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