如何在PHP类中使用构造函数的详细教程？

class MyClass {
  public $property1;
  private $property2;

  public function __construct($value1, $value2) {
    $this->property1 = $value1;
    $this->property2 = $value2;
    echo "MyClass 构造函数被调用，property1: " . $this->property1 . ", property2: " . $this->property2 . "\n";
  }

  public function getProperty2() {
    return $this->property2;
  }
}

$myObject = new MyClass("Hello", 123); // 输出: MyClass 构造函数被调用，property1: Hello, property2: 123
echo $myObject->property1 . "\n"; // 输出: Hello
echo $myObject->getProperty2() . "\n"; // 输出: 123

class MyClass {
  public function __construct($param1 = null, $param2 = null) {
    if ($param1 === null && $param2 === null) {
      // 没有参数的情况
      echo "No parameters provided.\n";
    } elseif ($param2 === null) {
      // 只有一个参数的情况
      echo "One parameter provided: " . $param1 . "\n";
    } else {
      // 两个参数的情况
      echo "Two parameters provided: " . $param1 . ", " . $param2 . "\n";
    }
  }
}

$obj1 = new MyClass(); // 输出: No parameters provided.
$obj2 = new MyClass("Value1"); // 输出: One parameter provided: Value1
$obj3 = new MyClass("Value1", "Value2"); // 输出: Two parameters provided: Value1, Value2

class ParentClass {
  public $parentProperty;

  public function __construct($value) {
    $this->parentProperty = $value;
    echo "ParentClass 构造函数被调用，parentProperty: " . $this->parentProperty . "\n";
  }
}

class ChildClass extends ParentClass {
  public $childProperty;

  public function __construct($parentValue, $childValue) {
    parent::__construct($parentValue); // 调用父类的构造函数
    $this->childProperty = $childValue;
    echo "ChildClass 构造函数被调用，childProperty: " . $this->childProperty . "\n";
  }
}

$childObject = new ChildClass("ParentValue", "ChildValue");
// 输出: ParentClass 构造函数被调用，parentProperty: ParentValue
// 输出: ChildClass 构造函数被调用，childProperty: ChildValue
echo $childObject->parentProperty . "\n"; // 输出: ParentValue
echo $childObject->childProperty . "\n"; // 输出: ChildValue

interface LoggerInterface {
  public function log(string $message);
}

class FileLogger implements LoggerInterface {
  private $filePath;

  public function __construct(string $filePath) {
    $this->filePath = $filePath;
  }

  public function log(string $message) {
    file_put_contents($this->filePath, $message . "\n", FILE_APPEND);
  }
}

class MyService {
  private $logger;

  public function __construct(LoggerInterface $logger) {
    $this->logger = $logger;
  }

  public function doSomething() {
    $this->logger->log("MyService is doing something.");
    echo "MyService is doing something.\n";
  }
}

$logger = new FileLogger("app.log");
$myService = new MyService($logger);
$myService->doSomething(); // 输出: MyService is doing something. (同时 "MyService is doing something." 被写入 app.log 文件)