What's the fastest way to compare two objects in PHP?

Question

Let's say I have an object - a User object in this case - and I'd like to be able to track changes to with a separate class. The User object should not have to change it's behavior in any way for this to happen.

Therefore, my separate class creates a "clean" copy of it, stores it somewhere locally, and then later can compare the User object to the original version to see if anything changed during its lifespan.

Is there a function, a pattern, or anything that can quickly compare the two versions of the User object?

Option 1 Maybe I could serialize each version, and directly compare, or hash them and compare?

Option 2 Maybe I should simply create a ReflectionClass, run through each of the properties of the class and see if the two versions have the same property values?

Option 3 Maybe there is a simple native function like objects_are_equal($object1,$object2);?

What's the fastest way to do this?

Answer 1

Simple example comparing dto class through reflection

class InvoiceDetails
{
    /** @var string */
    public $type;

    /** @var string */
    public $contractor;

    /** @var string */
    public $invoiceNumber;

    /** @var \DateTimeInterface|null */
    public $saleDate;

    /** @var \DateTimeInterface|null */
    public $issueDate;

    /** @var \DateTimeInterface|null */
    public $dueDate;

    /** @var string */
    public $payment;

    /** @var string */
    public $status;


    public function isEqual(InvoiceDetails $details): bool
    {
        $reflection = new \ReflectionClass(self::class);

        /** @var \ReflectionProperty $property */
        foreach ($reflection->getProperties() as $property) {
            $name = $property->getName();
            if ($this->$name !== $details->$name) {
                return false;
            }
        }

        return true;
    }

}

Answer 2

The only way to access the all (public, protected and private) properties of an object without modifying it is through reflection. You could, if you wanted to, clone the object before it's modified and then compare them by using the reflection functions to loop through the different properties of one of the two objects and comparing values. That would effectively tell you what properties have changed.

If all you care to see is whether or not the objects have changed, you can use the == or === operators. Have a look at the comparing objects section of PHP's documentation.

That said, wouldn't just be easier to keep track of what you've changed as you change them?