rfc:closures

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rfc:closures [2008/07/16 23:58] – example fixes chris_serfc:closures [2009/12/15 22:40] – Fix list numbering rquadling
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   * Date: 2008-07-01   * Date: 2008-07-01
   * Author: Christian Seiler <chris_se@gmx.net>, Dmitry Stogov <dmitry@zend.com>   * Author: Christian Seiler <chris_se@gmx.net>, Dmitry Stogov <dmitry@zend.com>
-  * Status: Accepted+  * Status: Implemented
  
 This RFC discusses the introduction of compile-time lambda functions and closures in PHP. This RFC discusses the introduction of compile-time lambda functions and closures in PHP.
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 Closures and lambda functions can make programming much easier in several ways: Closures and lambda functions can make programming much easier in several ways:
- 
 ==== Lambda Functions ==== ==== Lambda Functions ====
  
-Lambda functions allow the quick definition of throw-away functions that are not used elsewhere. Imaging for example a piece of code that needs to call preg_replace_callback(). Currently, there are three possibilities to achieve this: +Lambda functions allow the quick definition of throw-away functions that are not used elsewhere. Imagine for example a piece of code that needs to call preg_replace_callback(). Currently, there are three possibilities to achieve this: 
- +  - Define the callback function elsewhere. This distributes code that belongs together throughout the file and decreases readability. 
-   - Define the callback function elsewhere. This distributes code that belongs together throughout the file and decreases readability. +  - Define the callback function in-place (but with a name). In that case one has to use function_exists() to make sure the function is only defined once. Here, the additional if() around the function definition makes the source code difficult to read. Example code:<code php>
- +
-   - Define the callback function in-place (but with a name). In that case one has to use function_exists() to make sure the function is only defined once. Here, the additional if() around the function definition makes the source code difficult to read. Example code: +
- +
-<code php>+
    function replace_spaces ($text) {    function replace_spaces ($text) {
      if (!function_exists ('replace_spaces_helper')) {      if (!function_exists ('replace_spaces_helper')) {
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    }    }
 </code> </code>
- +  - Use the present create_function() in order to create a function at runtime. This approach has several disadvantages: First of all, syntax highlighting does not work because a string is passed to the function. It also compiles the function at run time and not at compile time so opcode caches can't cache the function.
-   - Use the present create_function() in order to create a function at runtime. This approach has several disadvantages: First of all, syntax highlighting does not work because a string is passed to the function. It also compiles the function at run time and not at compile time so opcode caches can't cache the function.+
  
 ==== Closures ==== ==== Closures ====
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 The following proposal and patch implement compile-time lambda functions and closures for PHP while keeping the patch as simple as possible. The following proposal and patch implement compile-time lambda functions and closures for PHP while keeping the patch as simple as possible.
- 
 ==== Userland perspective ==== ==== Userland perspective ====
  
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      return preg_replace_callback ('/( +) /', $replacement, $text);      return preg_replace_callback ('/( +) /', $replacement, $text);
    }    }
 +</code>
 +
 +You can even put the lambda function inline, for example:
 +
 +<code php>
 +  function replace_spaces ($text) {
 +    return preg_replace_callback ('/( +) /',
 +      function ($matches) {
 +        return str_replace ($matches[1], ' ', '&nbsp;').' ';
 +      }, $text);
 +  }
 </code> </code>
  
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 === Interaction with OOP === === Interaction with OOP ===
 +
 +$this support has been removed, see [[rfc/closures/removal-of-this|removal of this]]
  
 If a closure is defined inside an object, the closure has full access to the current object through $this (without the need to import it explicitly) and all private and protected methods of that class. This also applies to nested closures. Example: If a closure is defined inside an object, the closure has full access to the current object through $this (without the need to import it explicitly) and all private and protected methods of that class. This also applies to nested closures. Example:
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 In this case, $this is not available inside the closure. This may save a lot of memory if saves many closures that originated in longer needed objects. In this case, $this is not available inside the closure. This may save a lot of memory if saves many closures that originated in longer needed objects.
 +
  
 ==== Additional goody: _ _invoke ==== ==== Additional goody: _ _invoke ====
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 </code> </code>
  
-==== Interaction with reflection ====+==== Interaction with reflection (1) ====
  
 Since closures are anonymous, they do **not** appear in reflection. Since closures are anonymous, they do **not** appear in reflection.
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 $object->x = 5; $object->x = 5;
 $closure (); $closure ();
 +</code>
 +
 +==== Interaction with reflection (2) ====
 +
 +In addition to the previous patch, reflection support was augmented to support reflecting closure objects and returning the correct function pointer.
 +
 +<code php>
 +$closure = function ($a, &$b, $c = null) { };
 +$m = new ReflectionMethod ($closure, '__invoke');
 +Reflection::export ($m);
 +</code>
 +
 +This will yield:
 +
 +<code>
 +Method [ <internal> public method __invoke ] {
 +
 +  - Parameters [3] {
 +    Parameter #0 [ <required> $a ]
 +    Parameter #1 [ <required> &$b ]
 +    Parameter #2 [ <optional> $c ]
 +  }
 +}
 +</code>
 +
 +The following will also work (invoke is implied if no method name is specified):
 +
 +<code php>
 +$m = new ReflectionMethod ($closure);
 +$p = new ReflectionParameter ($closure, 0);
 +$p = new ReflectionParameter ($closure, 'a');
 +$p = new ReflectionParameter (array ($closure, '__invoke'), 0);
 </code> </code>
  
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 ===== Changelog ==== ===== Changelog ====
  
 +   * 2008-08-11 Christian Seiler: Documented additional reflection improvements (see php-internals)
    * 2008-07-15 Christian Seiler: Updated status of this RFC    * 2008-07-15 Christian Seiler: Updated status of this RFC
    * 2008-07-01 Christian Seiler: Updated patch yet again    * 2008-07-01 Christian Seiler: Updated patch yet again
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    * 2008-06-16 Christian Seiler: Small changes    * 2008-06-16 Christian Seiler: Small changes
    * 2008-06-16 Christian Seiler: Initial creation    * 2008-06-16 Christian Seiler: Initial creation
- 
rfc/closures.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1

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