如何在PHP中设置类变量？

Question

I have a class in php and want to know if there is a specific convention how to set these private variables in my constructor.

Should I set them with my setter or with this ?

class foo {

  private $bar;

  public function __construct($foobar) {
     $this->bar = $foobar;
  }

  public function setBar($bar) {
    $this->bar = $bar;
  }

  public function getBar() {
    return $this->bar;
  }
}

OR

class foo {

  private $bar;

  public function __construct($foobar) {
     $this->setBar($foobar);
  }

  public function setBar($bar) {
    $this->bar = $bar;
  }

  public function getBar() {
    return $this->bar;
  }
}

Or is my question just philosophical? Same question could be asked with getters . But I guess you have to use setters and getters when handling private variables of your parent class.

Answer 1

You should use the setBar in the constructor because of data validation, and future maintenance.

// a developer introduces a bug because the string has padding.
$foo->setBar("chickens   ");

// the developer fixes the bug by updating the setBar setter
public function setBar($bar) {
    $this->bar = trim($bar);
}

// the developer doesn't see this far away code
$f = new foo("chickens   ");

The developer sends the code to production thinking he fixed the bug.

Answer 2

In such a trivial example, yes your question is mostly philosophical! :) However, if your setter would perform some special actions (such like checking the validity of the input, or modifiying it), then I would recommend to use the second scheme.

Answer 3

This:

  class foo {

  private $bar;

  public function __construct($foobar) {
     $this->bar = $foobar;
  }

  public function setBar($bar) {
    $this->bar = $bar;
  }

  public function getBar() {
    return $this->bar;
  }
}

is no different than this:

class foo{

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

 public $bar;

One reason to use a getter and a setter is if you only allow a variable to be set on object construction like the following:

class foo {

  private $bar;

  public function __construct($foobar) {
     $this->bar = $foobar;
  }


  public function getBar() {
    return $this->bar;
  }
}

So don't overuse getters and setters unless necessary