从5.4版开始，PHP支持trait。这并不是你真正想要的，但基于特征的简单方法是:

trait StudentTrait {
    protected $id;
    protected $name;

    final public function setId($id) {
        $this->id = $id;
        return $this;
    }

    final public function getId() { return $this->id; }

    final public function setName($name) {
        $this->name = $name; 
        return $this;
    }

    final public function getName() { return $this->name; }

}

class Student1 {
    use StudentTrait;

    final public function __construct($id) { $this->setId($id); }
}

class Student2 {
    use StudentTrait;

    final public function __construct($id, $name) { $this->setId($id)->setName($name); }
}

我们最终得到两个类，每个构造函数一个，这有点适得其反。为了保持理智，我将加入一个工厂:

class StudentFactory {
    static public function getStudent($id, $name = null) {
        return 
            is_null($name)
                ? new Student1($id)
                : new Student2($id, $name)
    }
}

所以，这一切都归结为:

$student1 = StudentFactory::getStudent(1);
$student2 = StudentFactory::getStudent(1, "yannis");

这是一个非常冗长的方法，但它可以非常方便。

从PHP 8开始，我们可以使用命名参数:

class Student {

  protected int $id;
  protected string $name;

  public function __construct(int $id = null, string $name = null, array $row_from_database = null) {
    if ($id !== null && $name !== null && $row_from_database === null) {
      $this->id = $id;
      $this->name = $name;
    } elseif ($id === null && $name === null
        && $row_from_database !== null
        && array_keys($row_from_database) === [ 'id', 'name' ]
        && is_int($row_from_database['id'])
        && is_string($row_from_database['name'])) {
      $this->id = $row_from_database['id'];
      $this->name = $row_from_database['name'];
    } else {
      throw new InvalidArgumentException('Invalid arguments');
    }
  }

}

$student1 = new Student(id: 3, name: 'abc');
$student2 = new Student(row_from_database: [ 'id' => 4, 'name' => 'def' ]);

通过适当的检查，可以排除无效的参数组合，这样创建的实例在构造函数的末尾是一个有效的实例(但错误只会在运行时检测到)。

public function __construct() {
    $parameters = func_get_args();
    ...
}

$o = new MyClass('One', 'Two', 3);

现在$ parameters将是一个值为'One'， 'Two'， 3的数组。

编辑,

我可以加上

func_num_args()

会给出函数的参数个数。

你总是可以在构造函数中添加一个额外的参数，比如mode，然后对它执行一个switch语句……

class myClass 
{
    var $error ;
    function __construct ( $data, $mode )
    {
        $this->error = false
        switch ( $mode )
        {
            'id' : processId ( $data ) ; break ;
            'row' : processRow ( $data ); break ;
            default : $this->error = true ; break ;
         }
     }

     function processId ( $data ) { /* code */ }
     function processRow ( $data ) { /* code */ }
}

$a = new myClass ( $data, 'id' ) ;
$b = new myClass ( $data, 'row' ) ;
$c = new myClass ( $data, 'something' ) ;

if ( $a->error )
   exit ( 'invalid mode' ) ;
if ( $b->error )
   exit ('invalid mode' ) ;
if ( $c->error )
   exit ('invalid mode' ) ;

Also with that method at any time if you wanted to add more functionality you can just add another case to the switch statement, and you can also check to make sure someone has sent the right thing through - in the above example all the data is ok except for C as that is set to "something" and so the error flag in the class is set and control is returned back to the main program for it to decide what to do next (in the example I just told it to exit with an error message "invalid mode" - but alternatively you could loop it back round until valid data is found).

为了回应Kris的最佳答案(顺便说一句，他帮助我设计了自己的课程)，这里有一个修改过的版本，供那些可能会觉得有用的人使用。包括用于从任何列中进行选择和从数组中转储对象数据的方法。干杯!

public function __construct() {
    $this -> id = 0;
    //...
}

public static function Exists($id) {
    if (!$id) return false;
    $id = (int)$id;
    if ($id <= 0) return false;
    $mysqli = Mysql::Connect();
    if (mysqli_num_rows(mysqli_query($mysqli, "SELECT id FROM users WHERE id = " . $id)) == 1) return true;
    return false;
}

public static function FromId($id) {
    $u = new self();
    if (!$u -> FillFromColumn("id", $id)) return false;
    return $u;
}

public static function FromColumn($column, $value) {
    $u = new self();
    if (!$u -> FillFromColumn($column, $value)) return false;
    return $u;
}

public static function FromArray($row = array()) {
    if (!is_array($row) || $row == array()) return false;
    $u = new self();
    $u -> FillFromArray($row);
    return $u;
}

protected function FillFromColumn($column, $value) {
    $mysqli = Mysql::Connect();
    //Assuming we're only allowed to specified EXISTENT columns
    $result = mysqli_query($mysqli, "SELECT * FROM users WHERE " . $column . " = '" . $value . "'");
    $count = mysqli_num_rows($result);
    if ($count == 0) return false;
    $row = mysqli_fetch_assoc($result);
    $this -> FillFromArray($row);
}

protected function FillFromArray(array $row) {
    foreach($row as $i => $v) {
        if (isset($this -> $i)) {
            $this -> $i = $v;
        }
    }
}

public function ToArray() {
    $m = array();
    foreach ($this as $i => $v) {
        $m[$i] = $v;    
    }
    return $m;
}

public function Dump() {
    print_r("<PRE>");
    print_r($this -> ToArray());
    print_r("</PRE>");  
}

正如在其他评论中所述，由于PHP不支持重载，通常会避免构造函数中的“类型检查技巧”，而是使用工厂模式

ie.

$myObj = MyClass::factory('fromInteger', $params);
$myObj = MyClass::factory('fromRow', $params);