PHP Doc comment after unserialization - php

Question

The ReflectionMethod instance from PHP (http://php.net/manual/en/class.reflectionmethod.php) has the getDocComment method that returns the annotation of a method. This works ok, unless you use unserialized object.
$ref = new ReflectionClass('a');
var_dump(method_exists($ref, 'getDocComment')); //bool(true)
var_dump($ref->getDocComment()); //bool(false)
$ref = unserialize(serialize($ref));
var_dump(method_exists($ref, 'getDocComment')); //bool(true)
var_dump($ref->getDocComment()); //PHP Warning: Uncaught Error: Internal error: Failed to retrieve the reflection object
Is there any way of testing if the ReflectionMethod object has correctly defined doc comment? I mean, I do not care about getting the annotation after serialize/unserialize, but I want to check if calling getDocComment is safe.
Edit: According to responses that advice error handling + fallback, I rephrase the Q.
I have some simple cache of reflections (array of ReflectionMethod objects). Until I use item from that cache, I wold like to chech its correctness. I do NOT want to handle error, I want to "predict error". Awesome would be something like hasDocComment method that does not generate any error, but returns only true/false within any ReflectionMethod object state.

Answer 1

The general approach of serializing reflection objects is wrong. There exists a PHP Bug report for it, but it has been set to "irrelevant":
https://bugs.php.net/bug.php?id=70719
The reason is, that you cannot connect a reflection object back to its class again, because you would have to deal with source code changes and all kinds of stuff. What you should do instead is, to serialize the name of the class and generate a NEW reflection object from that class, when you unserialize.
Code Example:
class A { }
$ref = new ReflectionClass('A');
var_dump(method_exists($ref, 'getDocComment'));
// serialize only the class name
$refClass = unserialize(serialize($ref->getName()));
// get a new reflection object from that class ...
$ref = new ReflectionClass($refClass);
var_dump(method_exists($ref, 'getDocComment'));
// If you want to serialize an object
$a = new A();
$a2 = unserialize(serialize($a));
$ref = new ReflectionClass(get_class($a2));
var_dump(method_exists($ref, 'getDocComment'));

Answer 2

If you need to be able to handle errors, you can try/catch the execution block. Since alt-php71-7.1.0-1 (which you seem to be using), this will throw an instance of Error instead of simply a Fatal Error, which allows you to do error handling.
<?php
class A { }
$ref = new ReflectionClass('A');
var_dump(method_exists($ref, 'getDocComment')); //bool(true)
var_dump($ref->getDocComment()); //bool(false)
// serialize only the class name
$refClass = unserialize(serialize($ref));
try {
$refClass->getDocComment();
// do your work
}
catch (Error $e) {
echo "Malformed Reflection object: ".$e->getMessage();
}
Demo
And since you can still get the class name from the malformed Reflection instance, you can instantiate a new one right in your catch block:
<?php
class A { }
$ref = new ReflectionClass('A');
var_dump(method_exists($ref, 'getDocComment')); //bool(true)
var_dump($ref->getDocComment()); //bool(false)
// serialize only the class name
$refClass = unserialize(serialize($ref));
try {
$refClass->getDocComment();
}
catch (Error $e) {
$recoveredRef = new ReflectionClass($refClass->getName());
var_dump($recoveredRef);
var_dump($recoveredRef->getDocComment()); // works correctly
echo "Malformed Reflection object, but recovered: ".$e->getMessage();
}
Demo