Anonymous Classes, Generators and Closures in PHP 7

PHP 7 codebases often use anonymous classes (new class implements Logger {}) for quick test doubles, generators with yield from and return values (7.0), and closures with Closure::fromCallable() (7.1) or $closure->call($obj) (7.0). Recognizing these lets you maintain them and later replace some with PHP 8 equivalents like first-class callable syntax.

<?php
$logger = new class implements LoggerInterface {
    use Psr\Log\LoggerTrait;
    public array $records = [];
    public function log($level, $message, array $context = []): void
    {
        $this->records[] = [$level, $message];
    }
};

function numbers(): Generator
{
    yield 1;
    yield from [2, 3];
    return 3;                      // retrieve with ->getReturn()
}

$validator = Closure::fromCallable([$this, 'validate']);   // PHP 8.1: $this->validate(...)

Common pitfalls

• Using anonymous classes for production services, making them hard to reference and test.
• Calling getReturn() before a generator has finished.
• Binding closures to objects (bindTo) in ways that hide dependencies.

Key points

• Anonymous classes suit quick test doubles
• Generators support yield from and return values
• Closure::fromCallable → first-class callables in PHP 8.1

Further reading: PHP manual: anonymous classes