抽象类 #

<?php
abstract class Animal
{
    protected string $name;
    
    public function __construct(string $name)
    {
        $this->name = $name;
    }
    
    abstract public function speak(): string;
    
    public function move(): string
    {
        return "{$this->name} is moving";
    }
}

<?php
class Dog extends Animal
{
    public function speak(): string
    {
        return "{$this->name} says Woof!";
    }
}

class Cat extends Animal
{
    public function speak(): string
    {
        return "{$this->name} says Meow!";
    }
}

<?php
abstract class DataExporter
{
    final public function export(array $data): string
    {
        $formatted = $this->format($data);
        return $this->output($formatted);
    }
    
    abstract protected function format(array $data): string;
    
    protected function output(string $data): string
    {
        return $data;
    }
}

class CsvExporter extends DataExporter
{
    protected function format(array $data): string
    {
        $lines = [];
        foreach ($data as $row) {
            $lines[] = implode(',', $row);
        }
        return implode("\n", $lines);
    }
}