rfc:isset_ternary

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
rfc:isset_ternary [2014/09/16 18:30] – v0.2 - Overhauled proposal, proposing new operator ''??'' instead of an extension to ''?:'' ajfrfc:isset_ternary [2017/09/22 13:28] (current) – external edit 127.0.0.1
Line 1: Line 1:
 ====== PHP RFC: Null Coalesce Operator ====== ====== PHP RFC: Null Coalesce Operator ======
-  * Version: 0.2 +  * Version: 0.2.3 
-  * Date: 2014-09-06, last updates 2014-09-16 +  * Date: 2014-09-06, last updated 2014-09-16 
-  * Author: Andrea Faulds, ajf@ajf.me +  * Author: Andrea Faulds <ajf@ajf.me> 
-  * Status: Under Discussion+  * Contributor: Nikita Popov <nikic@php.net> (initial patch) 
 +  * Status: Implemented (PHP 7)
   * First Published at: http://wiki.php.net/rfc/isset_ternary   * First Published at: http://wiki.php.net/rfc/isset_ternary
  
Line 9: Line 10:
 ===== Introduction ===== ===== Introduction =====
  
-PHP is a web-focussed programming language, so processing user data is a frequent activity. In such processing it is common to check for something's existence, and if it doesn't exist, use a default value. Yet the simplest way to do this, something along the lines of ''isset($_GET['mykey']) ? $_GET['mykey'] : ""'', is unnecessarily cumbersome. The short ternary operator, ''?:'' provides a way to do this much more conveniently: ''$_GET['mykey'] ? ""''. However, this is not good practise, as if the value does not exist it will raise an ''E_NOTICE''. Because of these issues, some sort of ifsetor() operator or a modification to ''?:'''s behaviour to make this common pattern easier has been a frequent request (See References).+PHP is a web-focussed programming language, so processing user data is a frequent activity. In such processing it is common to check for something's existence, and if it doesn't exist, use a default value. Yet the simplest way to do this, something along the lines of ''<nowiki>isset($_GET['mykey']) ? $_GET['mykey'] : ""</nowiki>'', is unnecessarily cumbersome. The short ternary operator, ''?:'' provides a way to do this much more conveniently: ''<nowiki>$_GET['mykey'] ?: ""</nowiki>''. However, this is not good practice, as if the value does not exist it will raise an ''E_NOTICE''. Because of these issues, some sort of ifsetor() operator or a modification to ''?:'''s behaviour to make this common pattern easier has been a frequent request (See References).
  
 ===== Proposal ===== ===== Proposal =====
  
-The coalesce, or ''??'', operator is added, which returns the result of its first operand if it exists and is not NULL, or else its second operand. This means the ''$_GET['mykey'] ?? ""'' is completely safe and will not raise an E_NOTICE. Some examples of its use:+The coalesce, or ''??'', operator is added, which returns the result of its first operand if it exists and is not NULL, or else its second operand. This means the ''<nowiki>$_GET['mykey'] ?? ""</nowiki>'' is completely safe and will not raise an E_NOTICE. Some examples of its use:
  
 <code php> <code php>
 // Fetches the request parameter user and results in 'nobody' if it doesn't exist // Fetches the request parameter user and results in 'nobody' if it doesn't exist
-$username = $_GET['user'] ?? 'nobody'; // equivalent to: $username = isset($_GET['user']) ? $_GET['user'] : 'nobody';+$username = $_GET['user'] ?? 'nobody'; 
 +// equivalent to: $username = isset($_GET['user']) ? $_GET['user'] : 'nobody';
  
 // Calls a hypothetical model-getting function, and uses the provided default if it fails // Calls a hypothetical model-getting function, and uses the provided default if it fails
-$model = Model::get($id) ?? $default_model; // equivalent to: ; (($model = Model::get($id)) === NULL) { $model = $default_model; }+$model = Model::get($id) ?? $default_model; 
 +// equivalent to: if (($model = Model::get($id)) === NULL) { $model = $default_model; }
  
 // Parse JSON image metadata, and if the width is missing, assume 100 // Parse JSON image metadata, and if the width is missing, assume 100
 $imageData = json_decode(file_get_contents('php://input')); $imageData = json_decode(file_get_contents('php://input'));
 $width = $imageData['width'] ?? 100; $width = $imageData['width'] ?? 100;
 +// equivalent to: $width = isset($imageData['width']) ? $imageData['width'] : 100;
 </code> </code>
  
-===== Proposed PHP Version(s) =====+It can even be chained:
  
-This proposed for the next PHP x, which at the time of this writing would be PHP 7.+<code php> 
 +$x = NULL; 
 +$y = NULL; 
 +$z = 3; 
 +var_dump($x ?? $y ?? $z); // int(3)
  
 +$x = ["yarr" => "meaningful_value"];
 +var_dump($x["aharr"] ?? $x["waharr"] ?? $x["yarr"]); // string(16) "meaningful_value"
 +</code>
  
-===== Proposed Voting Choices =====+This example demonstrates the precedence relative to the ternary operator and the boolean or operator, which is the same as C#:
  
-As this is a language change, a 2/3 majority is required. A straight Yes/No vote would be held.+<code php> 
 +var_dump(2 ?? 3 ? 4 : 5);      // (2 ?? 3) ? 4 : 5        => int(4) 
 +var_dump(0 || 2 ?? 3 ? 4 : 5); // ((0 || 2) ?? 3) ? 4 : 5 => int(4) 
 +</code> 
 + 
 +This example demonstrates how it is a short-circuiting operator: 
 + 
 +<code php> 
 +function foo() { 
 +    echo "executed!", PHP_EOL; 
 +} 
 +var_dump(true ?? foo()); // outputs bool(true), "executed!" does not appear as it short-circuited 
 +</code> 
 + 
 +===== Proposed PHP Version(s) ===== 
 + 
 +This proposed for the next PHP x, which at the time of this writing would be PHP 7.
  
 ===== Patches and Tests ===== ===== Patches and Tests =====
Line 41: Line 68:
  
 The original patch was graciously provided by Nikita Popov. The original patch was graciously provided by Nikita Popov.
 +
 +===== Vote =====
 +
 +As this is a language change, a 2/3 majority is required. A straight Yes/No vote is being held.
 +
 +Voting started on 2014-09-20 and ended on 2014-09-27.
 +
 +<doodle title="Approve Null Coalesce Operator RFC and merge patch into master?" auth="ajf" voteType="single" closed="true">
 +   * Yes
 +   * No
 +</doodle>
  
 ===== Implementation ===== ===== Implementation =====
-After the project is implemented, this section should contain  + 
-  - the version(s) it was merged to +Merged into master (which will be PHP 7): https://github.com/php/php-src/commit/2d069f640e6cccfa3ba8b1e4f375ade20fb33f64 
-  - a link to the git commit(s) + 
-  - a link to the PHP manual entry for the feature+Documented at: http://php.net/manual/en/language.operators.comparison.php
  
 ===== References ===== ===== References =====
Line 62: Line 100:
  
 This list is quite probably incomplete. This list is quite probably incomplete.
 +
 +Operator precedence in C#: http://msdn.microsoft.com/en-us/library/6a71f45d.aspx
  
 ===== Rejected Features ===== ===== Rejected Features =====
 Keep this updated with features that were discussed on the mail lists. Keep this updated with features that were discussed on the mail lists.
 +
 +===== Errata =====
 +
 +The name of this RFC [[http://blog.ajf.me/2015-12-07-poorly-named-rfcs|ought to have been "null coalescing operator", not "null coalesce operator"]].
  
 ===== Changelog ===== ===== Changelog =====
  
-* v0.2 - Overhauled proposal, proposing new operator ''??'' instead of an extension to ''?:'' +  * (2016-03-13) Added Errata 
-* v0.1 - Created+  * v0.2.3 - Added short-circuit example 
 +  * v0.2.2 - Added precedence example 
 +  * v0.2.1 - Added chaining example 
 +  * v0.2 - Overhauled proposal, proposing new operator ''??'' instead of an extension to ''?:'' 
 +  * v0.1 - Created
rfc/isset_ternary.1410892202.txt.gz · Last modified: 2017/09/22 13:28 (external edit)

Page Tools