PHP ReflectionReference::getId() Method: Usage and Examples

When building tools that inspect PHP code, ReflectionReference::getId() helps answer a focused question: returns a unique binary identifier for a reference within the running process.

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

What Is ReflectionReference::getId()?

Returns a unique binary identifier for a reference within the running process.

Its method signature is:

public function getId(): string

This method has no required arguments.

Return value: string

Example 1: Inspect the basic behavior

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

<?php

declare(strict_types=1);

$total = 10;
$record = ["total" => &$total, "description" => "report"];
$referenceReflection = ReflectionReference::fromArrayElement($record, "total");

$result = $referenceReflection->getId();
echo strlen($result) . " bytes of reference ID";

Output:

20 bytes of reference ID

Explanation: Returns a unique binary identifier for a reference within the running process.

Example 2: Compare a second case

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

<?php

declare(strict_types=1);

$total = 11;
$record = ["total" => &$total, "description" => "report"];
$referenceReflection = ReflectionReference::fromArrayElement($record, "total");

$result = $referenceReflection->getId();
echo strlen($result) . " bytes of reference ID";

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

Output:

20 bytes of reference ID
Result type: string

Explanation: The ID is binary and should not be stored as a stable cross-request identifier.

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);

$total = 12;
$record = ["total" => &$total, "description" => "report"];
$referenceReflection = ReflectionReference::fromArrayElement($record, "total");

$result = $referenceReflection->getId();
echo strlen($result) . " bytes of reference ID";

// 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:

20 bytes of reference ID
Reflection result available

Explanation: fromArrayElement finds a reference in an array.

Important Behavior and Edge Cases

• The ID is binary and should not be stored as a stable cross-request identifier.
• fromArrayElement finds a reference in an array.
• 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 a unique binary identifier for a reference within the running process.
• The ID is binary and should not be stored as a stable cross-request identifier.
• fromArrayElement finds a reference in an array.

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