PHP OOP：对象属性的值可以是函数吗？

Question

My question is quite simple: In PHP OOP I want the value of an object property to be returned by a function . To be specific: I want a string to be translated with gettext. But it seems, that the value of a property has to be a string, a number or an array but not a function.

1. Why is that so?
2. Is there a solution for my need to have the value translated?

My code is similar to this:

<?php
class Bar extends Foo {
  public $baz = array('lorem' => __('ipsum'));

  // other code
?>

Answer 1

If you look at the manual regarding properties , you will see that:

This declaration may include an initialization, but this initialization must be a constant value--that is, it must be able to be evaluated at compile time and must not depend on run-time information in order to be evaluated.

So you cannot use a function when you declare the property.

However, the value can be set somewhere else, so in your case you could set it for example in the constructor:

<?php
class Bar extends Foo {
  public $baz;

  function __construct()
  {
     $this->baz = array('lorem' => __('ipsum'));
  }

  // other code
?>

Answer 2

Properties in PHP for classes must be a scalar value, therefore, you cannot expect to call a function as the property value. To properly to do this, you would need to set the value in the constructor.

<?php
class Bar extends Foo {
  public $baz = array('lorem' => NULL);

  public function __construct() 
  {
    $this->baz['lorem'] = __('ipsum')
  }
?>