rfc:variadics

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rfc:variadics [2013/08/28 19:57] nikicrfc:variadics [2017/09/22 13:28] (current) – external edit 127.0.0.1
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   * Date: 2013-08-27   * Date: 2013-08-27
   * Author: Nikita Popov <nikic@php.net>   * Author: Nikita Popov <nikic@php.net>
-  * Status: Under Discussion +  * Status: Implemented in PHP 5.6 ([[https://github.com/php/php-src/commit/0d7a6388663b76ebed6585ac92dfca5ef65fa7af|git:0d7a6388]])
-  * Proposed for: PHP 5.6+
   * Patch: https://github.com/php/php-src/pull/421   * Patch: https://github.com/php/php-src/pull/421
 +  * Mailing list discussion: http://markmail.org/message/uhewgv7zaagkgzdv
  
 ===== Proposal ===== ===== Proposal =====
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 The ''%%...$params%%'' syntax indicates that this is a variadic function and that all arguments after ''$query'' should be put into the ''$params'' array. Using the new syntax both of the issues mentioned above are solved. The ''%%...$params%%'' syntax indicates that this is a variadic function and that all arguments after ''$query'' should be put into the ''$params'' array. Using the new syntax both of the issues mentioned above are solved.
 +
 +==== Population of variadic parameter ====
 +
 +The following example shows how the variadic parameter ''%%...$params%%'' is populated depending on the number of passed arguments:
 +
 +<code php>
 +function fn($reqParam, $optParam = null, ...$params) {
 +    var_dump($reqParam, $optParam, $params);
 +}
 +
 +fn(1);             // 1, null, []
 +fn(1, 2);          // 1, 2, []
 +fn(1, 2, 3);       // 1, 2, [3]
 +fn(1, 2, 3, 4);    // 1, 2, [3, 4]
 +fn(1, 2, 3, 4, 5); // 1, 2, [3, 4, 5]
 +</code>
 +
 +''$params'' will be an empty array if the number of passed arguments is smaller than the number of declared parameters. Any further arguments will be added to the ''$params'' array (in the order in which they were passed). The ''$params'' array is using continuous zero-based indices.
  
 ==== By-reference capture ==== ==== By-reference capture ====
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 <code php> <code php>
 class MySQL implements DB { class MySQL implements DB {
-    public function prepare($query, &... $params) {+    public function prepare($query, &...$params) {
         $stmt = $this->pdo->prepare($query);         $stmt = $this->pdo->prepare($query);
         foreach ($params as $i => &$param) {         foreach ($params as $i => &$param) {
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 <code php> <code php>
-function array_merge(array... $arrays) { /* ... */ }+function array_merge(array ...$arrays) { /* ... */ }
 </code> </code>
  
-PHP would make sure that all arguments are actually arrays. This also works for all other typehints like ''%%callable... $callbacks%%'' or ''%%Route... $routes%%''.+PHP would make sure that all arguments are actually arrays. This also works for all other typehints like ''%%callable ...$callbacks%%'' or ''%%Route ...$routes%%''.
  
 ==== Prototype checks ==== ==== Prototype checks ====
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   * ''%%function fn($arg, &...$args)%%'': Do the capture by reference   * ''%%function fn($arg, &...$args)%%'': Do the capture by reference
   * ''%%function fn($arg, array ...$args)%%'': Enforce that all variadic arguments are arrays (or some other typehint)   * ''%%function fn($arg, array ...$args)%%'': Enforce that all variadic arguments are arrays (or some other typehint)
-  * ''%%function fn($arg, array& ...$args)%%'': Combine both - variadic arguments are arrays that are captured by-reference+  * ''%%function fn($arg, array &...$args)%%'': Combine both - variadic arguments are arrays that are captured by-reference
  
 The advantages of the syntax are: The advantages of the syntax are:
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 ==== Userland ==== ==== Userland ====
  
-This change does not break backwards comparability for userland code.+This change does not break backwards compatibility for userland code.
  
 In particular, this RFC does not propose to deprecate or remove the ''func_get_args()'' family of functions, at least not any time soon. In particular, this RFC does not propose to deprecate or remove the ''func_get_args()'' family of functions, at least not any time soon.
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   * ''%%$args...%%''. With ref-modifier (''%%&$args...%%'') this does not show well that the individual arguments are references, rather than ''$args'' itself. With typehint (''%%array $args...%%'') it also looks like the typehint applies to ''$args'' itself rather than all variadic arguments.   * ''%%$args...%%''. With ref-modifier (''%%&$args...%%'') this does not show well that the individual arguments are references, rather than ''$args'' itself. With typehint (''%%array $args...%%'') it also looks like the typehint applies to ''$args'' itself rather than all variadic arguments.
-  * ''*$args''. This is the syntax that both Ruby and Python use. For PHP this does not work well because ''*$'' is a weird combination. It gets worse with a by-reference capture: ''&*$args''. This looks like a random sequences of special characters.+  * ''*$args''. This is the syntax that both Ruby and Python use. For PHP this does not work well because ''*$'' is a weird combination. It gets worse with a by-reference capture: ''&*$args''. This looks like a random sequences of special characters. Combined with a typehint the syntax looks a lot like a pointer: ''Foo *$args''.
   * ''params $args''. This is what C# does. This would require making ''params'' a keyword. Furthermore this doesn't have any nice way to declare typehints. In C# this is done using ''params type[] args'', but PHP doesn't have ''type[]'' hints and introducing them only here doesn't seem right.   * ''params $args''. This is what C# does. This would require making ''params'' a keyword. Furthermore this doesn't have any nice way to declare typehints. In C# this is done using ''params type[] args'', but PHP doesn't have ''type[]'' hints and introducing them only here doesn't seem right.
    
-The proposed syntax is also used by Java and will be used in [[http://wiki.ecmascript.org/doku.php?id=harmony:rest_parameters|Javascript (ECMAScript Harmony proposal)]].+The proposed syntax is also used by Java and will be used in [[http://wiki.ecmascript.org/doku.php?id=harmony:rest_parameters|Javascript (ECMAScript Harmony proposal)]]. Go and C++ also employ a similar syntax.
  
 ===== Patch ===== ===== Patch =====
  
 Patch available in PR#421: https://github.com/php/php-src/pull/421 Patch available in PR#421: https://github.com/php/php-src/pull/421
 +
 +===== Vote =====
 +
 +The vote started on 16.09.2013 and ended on 23.09.2013. There were 36 votes in favor and one against, as such the necessary two-third majority is met and this feature is **accepted**.
 +
 +<doodle title="Should the proposed variadic-function syntax be added in PHP 5.6 (master)?" auth="nikic" voteType="single" closed="true">
 +   * Yes
 +   * No
 +</doodle>
  
 ===== Argument unpacking ===== ===== Argument unpacking =====
  
-A related syntactical element is the "splat" or "scatter" operator:+The [[rfc:argument_unpacking|argument unpacking RFC]] introduces the following related syntax:
  
 <code php> <code php>
 $db->query($query, ...$params); $db->query($query, ...$params);
 </code> </code>
- 
-This operator would unpack an array into an argument list (similarly to ''call_user_func_array''). It is not part of this RFC, but I plan to implement this in a separate proposal. 
rfc/variadics.1377719828.txt.gz · Last modified: 2017/09/22 13:28 (external edit)