__serialize and __unserialize in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the __serialize magic method in PHP?

The __serialize method allows an object to specify how it should be converted into an array for serialization. It returns an array of the object's data to be saved.

beginner

What does the __unserialize magic method do in PHP?

The __unserialize method receives an array of data and restores the object's properties from it when unserializing.

intermediate

How do __serialize and __unserialize improve over older serialization methods?

They provide a clear, explicit way to control what data is saved and restored, improving security and flexibility compared to __sleep and __wakeup.

beginner

Show a simple example of a class implementing <code>__serialize</code> and <code>__unserialize</code>.

class User {
  private string $name;
  private int $age;

  public function __construct(string $name, int $age) {
    $this->name = $name;
    $this->age = $age;
  }

  public function __serialize(): array {
    return ['name' => $this->name, 'age' => $this->age];
  }

  public function __unserialize(array $data): void {
    $this->name = $data['name'];
    $this->age = $data['age'];
  }
}

intermediate

Why might you want to customize serialization with __serialize and __unserialize?

To control exactly which properties are saved, avoid saving sensitive data, or transform data before saving and after loading.

What type of value must __serialize return?

A An object

B A string

C An array

D Null

__serialize must return an array representing the object's data.

Which method is called automatically when unserializing an object?

A __serialize

B __unserialize

C __wakeup

D __sleep

__unserialize is called to restore the object's state from an array.

What is a key advantage of using __serialize over __sleep?

A It allows returning an array of data instead of just property names

B It returns a string instead of an array

C It automatically encrypts data

D It disables serialization

__serialize returns an array of data, giving more control than __sleep which returns property names.

If you want to exclude a property from serialization, what should you do in __serialize?

A Throw an exception

B Include it with a null value

C Set it to false

D Omit it from the returned array

Simply omit the property from the array returned by __serialize to exclude it.

What PHP version introduced __serialize and __unserialize?

A PHP 7.4

B PHP 8.0

C PHP 5.6

D PHP 7.0

__serialize and __unserialize were introduced in PHP 7.4.

Explain how __serialize and __unserialize work together to save and restore an object's state.

Think about saving and loading data as a two-step process.

Describe a situation where customizing serialization with __serialize and __unserialize is useful.

Consider privacy or data format needs.