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Re: Class 'Model' not found

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Thomas 'PointedEars' Lahn <PointedEars@web.de> writes:

> 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*.

Great explanation, a wonderful reference for anyone needing to
understand these topics better.

-- 
Matthew Carter (m@ahungry.com)
http://ahungry.com

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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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