正如这里已经展示的，在PHP中有许多方法来声明多个构造函数，但是没有一种方法是正确的(因为PHP技术上不允许这样做)。 但这并不能阻止我们破解这个功能…… 下面是另一个例子:

<?php

class myClass {
    public function __construct() {
        $get_arguments       = func_get_args();
        $number_of_arguments = func_num_args();

        if (method_exists($this, $method_name = '__construct'.$number_of_arguments)) {
            call_user_func_array(array($this, $method_name), $get_arguments);
        }
    }

    public function __construct1($argument1) {
        echo 'constructor with 1 parameter ' . $argument1 . "\n";
    }

    public function __construct2($argument1, $argument2) {
        echo 'constructor with 2 parameter ' . $argument1 . ' ' . $argument2 . "\n";
    }

    public function __construct3($argument1, $argument2, $argument3) {
        echo 'constructor with 3 parameter ' . $argument1 . ' ' . $argument2 . ' ' . $argument3 . "\n";
    }
}

$object1 = new myClass('BUET');
$object2 = new myClass('BUET', 'is');
$object3 = new myClass('BUET', 'is', 'Best.');

使用和理解多个构造函数的最简单方法:

希望这能有所帮助。：）

你可以这样做:

public function __construct($param)
{
    if(is_int($param)) {
         $this->id = $param;
    } elseif(is_object($param)) {
     // do something else
    }
 }

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)。

我知道我在这方面非常晚，但我提出了一个相当灵活的模式，应该允许一些真正有趣和通用的实现。

像往常一样设置类，使用您喜欢的任何变量。

class MyClass{ protected $myVar1; protected $myVar2; public function __construct($obj = null){ if($obj){ foreach (((object)$obj) as $key => $value) { if(isset($value) && in_array($key, array_keys(get_object_vars($this)))){ $this->$key = $value; } } } } } When you make your object just pass an associative array with the keys of the array the same as the names of your vars, like so... $sample_variable = new MyClass([ 'myVar2'=>123, 'i_dont_want_this_one'=> 'This won\'t make it into the class' ]); print_r($sample_variable); The print_r($sample_variable); after this instantiation yields the following: MyClass Object ( [myVar1:protected] => [myVar2:protected] => 123 ) Because we've initialize $group to null in our __construct(...), it is also valid to pass nothing whatsoever into the constructor as well, like so... $sample_variable = new MyClass(); print_r($sample_variable); Now the output is exactly as expected: MyClass Object ( [myVar1:protected] => [myVar2:protected] => ) The reason I wrote this was so that I could directly pass the output of json_decode(...) to my constructor, and not worry about it too much. This was executed in PHP 7.1. Enjoy!

让我在这里加一粒沙子

我个人喜欢将构造函数作为返回类(对象)实例的静态函数添加。代码示例如下:

 class Person
 {
     private $name;
     private $email;

     public static function withName($name)
     {
         $person = new Person();
         $person->name = $name;

         return $person;
     }

     public static function withEmail($email)
     {
         $person = new Person();
         $person->email = $email;

         return $person;
     }
 }

注意，现在你可以像这样创建Person类的实例:

$person1 = Person::withName('Example');
$person2 = Person::withEmail('yo@mi_email.com');

我的代码来自:

http://alfonsojimenez.com/post/30377422731/multiple-constructors-in-php

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。