我可能会这样做:

<?php

class Student
{
    public function __construct() {
        // allocate your stuff
    }

    public static function withID( $id ) {
        $instance = new self();
        $instance->loadByID( $id );
        return $instance;
    }

    public static function withRow( array $row ) {
        $instance = new self();
        $instance->fill( $row );
        return $instance;
    }

    protected function loadByID( $id ) {
        // do query
        $row = my_awesome_db_access_stuff( $id );
        $this->fill( $row );
    }

    protected function fill( array $row ) {
        // fill all properties from array
    }
}

?>

然后，如果我想要一个学生，我知道ID:

$student = Student::withID( $id );

或者如果我有一个db行数组:

$student = Student::withRow( $row );

从技术上讲，您不需要构建多个构造函数，而只是静态帮助方法，但是这样可以避免构造函数中的大量意大利面条代码。

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!

按数据类型调用构造函数:

class A 
{ 
    function __construct($argument)
    { 
       $type = gettype($argument);

       if($type == 'unknown type')
       {
            // type unknown
       }

       $this->{'__construct_'.$type}($argument);
    } 

    function __construct_boolean($argument) 
    { 
        // do something
    }
    function __construct_integer($argument) 
    { 
        // do something
    }
    function __construct_double($argument) 
    { 
        // do something
    }
    function __construct_string($argument) 
    { 
        // do something
    }
    function __construct_array($argument) 
    { 
        // do something
    }
    function __construct_object($argument) 
    { 
        // do something
    }
    function __construct_resource($argument) 
    { 
        // do something
    }

    // other functions

} 

Kris的解决方案真的很好，但我更喜欢工厂和流畅风格的混合:

<?php

class Student
{

    protected $firstName;
    protected $lastName;
    // etc.

    /**
     * Constructor
     */
    public function __construct() {
        // allocate your stuff
    }

    /**
     * Static constructor / factory
     */
    public static function create() {
        return new self();
    }

    /**
     * FirstName setter - fluent style
     */
    public function setFirstName($firstName) {
        $this->firstName = $firstName;
        return $this;
    }

    /**
     * LastName setter - fluent style
     */
    public function setLastName($lastName) {
        $this->lastName = $lastName;
        return $this;
    }

}

// create instance
$student= Student::create()->setFirstName("John")->setLastName("Doe");

// see result
var_dump($student);
?>

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).

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。