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Re: OO PHP result of new if a constructor fails

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Christoph M. Becker wrote:

> Thomas 'PointedEars' Lahn wrote:
>> James Harris wrote:
>>> I understand that PHP constructors cannot return anything
>> Doubtful.
> 
> AIUI, a PHP constructor is the method __construct, […]

A common misconception (which was discussed during the ZCE PHP 5.4 Exam 
Preparation Course because it is a common pitfall in the exam).

Before there was the magic __construct() method (introduced with PHP 5.0), 
constructors could only be defined by a method whose identifier was the same 
as the class name, with the added catch that the matching was case-
insensitive (as with all PHP functions).

For backwards compatibility, this is still supported in PHP 5.x (just tested 
with PHP 5.6.2-1 CLI on Debian GNU/Linux); however, the __construct() method 
takes precedence for non-namespaced classes, and with namespaced classes the 
old behavior is no longer supported since PHP 5.3.3 (I, too, was at least 
not consciously aware of the latter – you can never learn enough).

<http://php.net/manual/en/language.oop5.decon.php>

Ad-hoc test code to play with:

  // namespace N;

  class C
  {
    function __construct ()
    {
      echo 42 . "\n";
    }
    
    function C ()
    {
      echo 23 . "\n";
    }
  }

  new C();

You should observe that

  * in PHP 5.x,

    - “23” is printed if you comment out the __construct() definition and
      leave the namespace declaration commented out;

    - *if the PHP version is greater than or equal to 5.3.3*,
      nothing is printed if you comment out the __construct() definition
      *and* use the namespace declaration;

    - “42” is printed otherwise;

  * in PHP 4.x (with the namespace declaration commented out, because it is
    a syntax error there),

    - “23” should be printed if you do not comment out the X() definition;

    - nothing should be printed otherwise.

> and that does not create an object, but merely initializes it, so the
> constructor can be thought of as a command (opposed to a query), and as
> such would never return anything (at least when properly called within a
> /new/ statement).

Since PHP 5.3.x at the latest, it is no longer possible to call constructors 
statically except with parent::…() [1], as that results in “Fatal error: 
Non-static method … cannot be called statically …” − 

<http://stackoverflow.com/a/19303354/855543>

lead me to find it in “zend_vm_execute.h” of PHP 5.3, but not PHP 5.2:

<http://lxr.php.net/search?q=cannot+be+called+statically&defs=&refs=&path=%2FPHP_5_3%2F&hist=&project=PHP_5_3>
<http://lxr.php.net/search?q=cannot+be+called+statically&defs=&refs=&path=%2FPHP_5_2%2F&hist=&project=PHP_5_2>

Also, it would appear that when a method is called as a constructor (with 
the “new” keyword; in the aforementioned PHP 5.6 version – may also be 
different in previous versions), its return value is ignored even if it is a 
reference to an object.  [Because of that, a constructor that can also serve 
as a factory, as in ECMAScript, for example, appears to be impossible in 
PHP.]
 
-- 
PointedEars
Zend Certified PHP Engineer
Twitter: @PointedEars2
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

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Thread

OO PHP result of new if a constructor fails "James Harris" <james.harris.1@gmail.com> - 2014-11-11 15:13 +0000
  Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-11 10:20 -0500
    Re: OO PHP result of new if a constructor fails "James Harris" <james.harris.1@gmail.com> - 2014-11-11 15:56 +0000
      Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-11 11:03 -0500
        Re: OO PHP result of new if a constructor fails "James Harris" <james.harris.1@gmail.com> - 2014-11-11 16:27 +0000
          Re: OO PHP result of new if a constructor fails Matthew Carter <m@ahungry.com> - 2014-11-11 12:01 -0500
            Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-11 12:56 -0500
          Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-11 12:52 -0500
  Re: OO PHP result of new if a constructor fails "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-11 18:12 +0100
  Re: OO PHP result of new if a constructor fails Richard Damon <Richard@Damon-Family.org> - 2014-11-11 13:03 -0500
  Re: OO PHP result of new if a constructor fails Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-11 23:54 +0100
    Re: OO PHP result of new if a constructor fails "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-12 03:00 +0100
      Re: OO PHP result of new if a constructor fails Matthew Carter <m@ahungry.com> - 2014-11-11 22:25 -0500
        Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-11 22:36 -0500
          Re: OO PHP result of new if a constructor fails Matthew Carter <m@ahungry.com> - 2014-11-12 01:30 -0500
            Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-12 07:08 -0500
            Re: OO PHP result of new if a constructor fails "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-12 13:30 +0100
              Re: OO PHP result of new if a constructor fails Denis McMahon <denismfmcmahon@gmail.com> - 2014-11-12 13:52 +0000
                Re: OO PHP result of new if a constructor fails "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-13 00:46 +0100
                Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-12 22:28 -0500
      Re: OO PHP result of new if a constructor fails Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-12 21:30 +0100
        Re: OO PHP result of new if a constructor fails "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-13 01:15 +0100
          Re: OO PHP result of new if a constructor fails Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-13 04:09 +0100
            Re: OO PHP result of new if a constructor fails Stefan+Usenet@Froehlich.Priv.at (Stefan Froehlich) - 2014-11-13 07:42 +0000
            Re: OO PHP result of new if a constructor fails "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-13 14:11 +0100
              Re: OO PHP result of new if a constructor fails Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-13 21:40 +0100
                Re: OO PHP result of new if a constructor fails "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-14 13:49 +0100
                Re: OO PHP result of new if a constructor fails Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-14 23:25 +0100
          Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-12 22:29 -0500
            Re: OO PHP result of new if a constructor fails Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-13 21:45 +0100
              Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-13 15:56 -0500
                Re: OO PHP result of new if a constructor fails Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-13 22:09 +0100
                Re: OO PHP result of new if a constructor fails Jerry Stuckle <jstucklex@attglobal.net> - 2014-11-13 21:03 -0500
              Re: OO PHP result of new if a constructor fails "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-13 22:47 +0100
                Re: OO PHP result of new if a constructor fails Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-13 22:59 +0100
                Re: OO PHP result of new if a constructor fails "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-18 19:02 +0100

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