Anonymous classes in PHP 7

I also found this useful when writing unit tests for traits so you can test only the trait method i.e.:

trait MyTrait 
{
    public method foo(): string
    {
        return 'foo';
    }
}
...
public function setUp(): void
{
    $this->testObject = (new class() {
        use MyTrait;
    });
}
public function testFoo(): void
{
    $this->assertEquals('foo', $this->testObject->foo());
}

You can find the information you are looking for here, where the RFC is presented.

The key points of the section "Use cases" are the following:

• Mocking tests becomes easy as pie. Create on-the-fly implementations for interfaces, avoiding using complex mocking APIs.
• Keep usage of these classes outside the scope they are defined in
• Avoid hitting the autoloader for trivial implementations