Hi internals, > I've created the RFC https://wiki.php.net/rfc/is_list > > This adds a new function `is_list(mixed $value): bool` that will return true > if the type of $value is array and the array keys are `0 .. count($value)-1` > in that order. > > It's well-known that PHP's `array` data type is rare among programming > languages > in that it supports both integer and string keys > and that iteration order is important and guaranteed. > (it is used for overlapping use cases - in many other languages, both > vectors/lists/arrays and hash maps are available) > > While it is possible to efficiently check that something is an array, > that array may still have string keys, not start from 0, have missing array > offsets, > or contain out of order keys. > > It can be useful to verify that the assumption that array keys are > consecutive integers is correct, > both for data that is being passed into a module or for validating data > before returning it from a module. > However, because it's currently inconvenient to do that, this has rarely been > done in my experience. > > In performance-sensitive serializers or data encoders, it may also be useful > to have an efficient check to distinguish lists from associative arrays. > For example, json_encode does this when deciding to serialize a value as [0, > 1, 2] instead of {“0”:0,“2”:1,“1”:1} > for arrays depending on the key orders. > > Prior email threads/PRs have had others indicate interest in the ability to > efficiently check > if a PHP `array` has sequential ordered keys starting from 0 > > https://externals.io/message/109760 “Any interest in a list type?” > https://externals.io/message/111744 “Request for couple memory optimized > array improvements” > Implementation: https://github.com/php/php-src/pull/6070 (some discussion is > in the linked PR it was based on)
Due to concerns about naming causing confusion with theoretical potential future changes to the language, I've updated https://wiki.php.net/rfc/is_list to use the name `is_array_and_list(mixed $value): bool` instead. (e.g. what if php used the reserved word `list` to add an actual list type in the future, and is_list() returned false for that.) I plan to start voting on the RFC in a few days. Thanks, - Tyson -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: https://www.php.net/unsub.php
