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Re: Class 'Model' not found

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Jerry Stuckle wrote:

> On 8/23/2016 1:23 AM, Matthew Carter wrote:
>> Jerry Stuckle <jstucklex@attglobal.net> writes:
>>> You've obviously not had the autoloading function pick up the wrong
>>> version of a class.  But that's not surprising from you.  You have
>>> repeatedly shown you have no concept of good coding techniques, and have
>>> probably never had two classes of ANY name on your system.
>> 
>> Why would you have 2 identically named classes in the same namespace (if
>> different namespaces, alias them)?
                         ^^^^^^^^^^ 
>> If you're actually referring to 2 versions of the same class at
>> different points in time, why not a VCS?
> 
> Because you loaded two different packages, both with the same class
> name.

You can have the same class name in the same namespace in two different 
*files*.

But you _can not_ have that in the same PHP program, not even as includes. 
It is not possible to redeclare classes, and you cannot undeclare/delete a 
class.  So it is irrelevant if you use an autoloader in that case.  For 
example,

  require_once 'Foo/Bar.php';
  require_once 'Baz/Bar.php';

where each Bar.php contains

  class Bar
  {
    // …
  }

results in “PHP Fatal error:  Cannot redeclare class Bar in … on line …”.  
No “use” statement can prevent that because the class has to be loaded 
*before* it can be aliased.  Which is why interoperable classes are declared 
in their own namespace these days (formerly, prefixes were used to avoid 
name collisions instead).

As for the same class in different namespaces, I have marked the important 
part in Matthew’s posting.  For further reference:

<http://php.net/manual/en/language.namespaces.importing.php>

IOW:

  /* or: use Foo\Bar\Baz */;
  use Foo\Bar\Baz as Bla;

  use Foo\Bar2\Baz as Blub;

Then there could be a “Foo/Bar/Baz.php” that contains
 
  namespace Foo\Bar;
 
  class Baz
  {
    // …
  }

and a “Foo/Bar2/Baz.php” that contains

  namespace Foo\Bar2;

  class Baz
  {
    // …
  }

and (with a suitable autoloader) you could just write

  /* or “new Baz()”, see above */
  new Bla();

  new Blub();

> Or you're running two different versions of software on the same machine.
> It's not at all uncommon when you're running multiple sites on one server.

If only you knew what you are talking about.

Different sites on the same machine, each using different versions of the 
same class, perhaps in the same namespace, would either use *different* 
autoloaders each (to avoid loading classes and their dependencies manually).  
This can be as simple as adapting the include_path per site, or as 
complicated as using different “require_once” statements (with different 
paths) to load the correct autoloader.

Or they would use one or more namespace-and-path-aware autoloaders.  It is 
possible to register *several* autoloaders, each only attempting to autoload 
the classes that are in its namespace.  Simple example:

  /* Library 1 code */

  function autoload_lib1 ($class)
  {
    echo "autoload_lib1: autoloading $class ...\n";
    if (strpos($class, "Lib1\\") !== 0)
    {
      trigger_error("DEBUG: autoload_lib1: autoloading of $class rejected: "
        . " Not in our namespace\n", E_USER_NOTICE);
      return;
    }

    /* Use include_once for the example only */
    include_once "lib1path" . DIRECTORY_SEPARATOR
      . str_replace("\\", DIRECTORY_SEPARATOR,
                    str_replace("Lib1\\", "", $class))
      . ".php";
  }

  spl_autoload_register("\\autoload_lib1", true);


  /* Library 2 code */

  function autoload_lib2 ($class)
  {
    echo "autoload_lib2: autoloading $class ...\n";
    if (strpos($class, "Lib2\\") !== 0)
    {
      trigger_error("DEBUG: autoload_lib1: autoloading of $class rejected: "
        . " Not in our namespace\n", E_USER_NOTICE);
      return;
    }

    /* Use include_once for the example only */
    include_once "lib2path" . DIRECTORY_SEPARATOR
      . str_replace("\\", DIRECTORY_SEPARATOR,
                    str_replace("Lib2\\", "", $class))
      . ".php";
  }

  spl_autoload_register("\\autoload_lib2", true);


  /* User code */

  new Lib1\Foo1();

[Usually it does not make sense to use two versions of the same library 
simultaneously because of different dependencies, and because the newer 
version can do more than the older one.  However, it is probably a good idea 
to always write an autoloader so that it does not attempt to autoload 
classes that are "out of its jurisdiction".]

It is also possible to have *one* autoloader that handles *several* 
namespaces and maps namespaces to paths correctly.  Simplest (as is, 
*unsafe*) case:

  function autoload_all ($class)
  {
    require_once str_replace("\\", DIRECTORY_SEPARATOR, $class) . ".php";
  }

  spl_autoload_register("\\autoload_all", true);

[Note that the autoloader can be in a namespace itself, which reduces the 
risk of namespace collisions for *its* declaration.  That also makes it 
easier to autoload only the classes "in the autoloader’s jurisdiction".]

IOW, the problems that you are presuming simply *do* *not* *exist*.
 
-- 
PointedEars
Zend Certified PHP Engineer 
<http://www.zend.com/en/yellow-pages/ZEND024953> | Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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Thread

Class 'Model' not found M desinger <info.nez@gmail.com> - 2016-08-21 07:35 -0700
  Re: Class 'Model' not found M desinger <info.nez@gmail.com> - 2016-08-21 07:36 -0700
  Re: Class 'Model' not found M desinger <info.nez@gmail.com> - 2016-08-21 07:43 -0700
    Re: Class 'Model' not found "J.O. Aho" <user@example.net> - 2016-08-21 18:08 +0200
      Re: Class 'Model' not found "Christoph M. Becker" <cmbecker69@arcor.de> - 2016-08-21 19:36 +0200
    Re: Class 'Model' not found Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-22 20:56 +0200
      Re: Class 'Model' not found Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-22 19:08 -0400
        Re: Class 'Model' not found Matthew Carter <m@ahungry.com> - 2016-08-23 01:23 -0400
          Re: Class 'Model' not found Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 08:07 -0400
            Re: Class 'Model' not found Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-27 14:26 +0200
              Re: Class 'Model' not found Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-27 10:13 -0400
                Re: Class 'Model' not found Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-28 02:12 +0200
                Re: Class 'Model' not found Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-27 20:32 -0400
              Re: Class 'Model' not found Matthew Carter <m@ahungry.com> - 2016-08-28 00:00 -0400
                Re: Class 'Model' not found Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-28 08:40 -0400
                Re: Class 'Model' not found Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-30 11:39 +0200
                Re: Class 'Model' not found Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-30 07:41 -0400
                Re: Class 'Model' not found Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-30 14:41 +0200
                Re: Class 'Model' not found Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-30 09:02 -0400
                Re: Class 'Model' not found Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-30 15:36 +0200
                Re: Class 'Model' not found Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-30 10:39 -0400
                Re: Class 'Model' not found Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-30 11:35 +0200
  Re: Class 'Model' not found M desinger <info.nez@gmail.com> - 2016-08-30 14:25 -0700
    Re: Class 'Model' not found Gregor Kofler <usenet@gregorkofler.com> - 2016-08-31 00:35 +0200
      Re: Class 'Model' not found M desinger <info.nez@gmail.com> - 2016-08-30 16:34 -0700
        Re: Class 'Model' not found Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-30 19:58 -0400

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