(PHP 8 >= 8.1.0)
array_is_list — 判断给定的 array 是否为 list
判断指定的 array 是否是 list。如果 array 的 key 由 0 到 count($array)-1 的连续数字组成，则该数组就是 list。
示例 #1 array_is_list() 示例
<?php
array_is_list([]); // true
array_is_list(['apple', 2, 3]); // true
array_is_list([0 => 'apple', 'orange']); // true
// key 未从 0 开始
array_is_list([1 => 'apple', 'orange']); // false
// key 的顺序不正确
array_is_list([1 => 'apple', 0 => 'orange']); // false
// 包含非整数 key
array_is_list([0 => 'apple', 'foo' => 'bar']); // false
// 非连续 key
array_is_list([0 => 'apple', 2 => 'bar']); // false
?>注意:
空数组也会返回
true。
Polyfills that call `array_keys()`, `array_values()` or `range()` are inefficient because they create new arrays unnecessarily.Please use this polyfill instead which creates no new arrays and only does a single pass over the given array.<?phpif (!function_exists("array_is_list")) { function array_is_list(array $array): bool { $i = 0; foreach ($array as $k => $v) { if ($k !== $i++) { return false; } } return true; }}?>slightly optimized version of phpnet at jesseschalken dot com's excellent array_is_list:<?phpif (!function_exists("array_is_list")) { function array_is_list(array $array): bool { $i = -1; foreach ($array as $k => $v) { ++$i; if ($k !== $i) { return false; } } return true; }}?>benchmarks: https://3v4l.org/9BPqLwhy is this faster you ask? because post-increment does more,here is what pre-increment actually means:step 1: increment the value by 1.step 2: return the value.here is what post-increment actually means:step 1: create a copy of the original value.step 2: increment the original value by 1.step 3: return the copy.another question might be "why didn't you write `if ($k !== ++$i) {` ? ... that is a good question! turns out that ++$i;if($k!==$i){...} is faster on PHP7 than if($k !== ++$i){...} for reasons unknown to me.. (if you have an answer, feel free to email me about it!) (i have NOT checked if PHP8/jit auto-optimize this stuff, but at least back in PHP7 it's true that pre-increment is faster than post-increment, and this polyfill is primarily for PHP7)Polyfill implementation for PHP versions lower than 8.1.<?phpif (!function_exists('array_is_list')){ function array_is_list(array $a) { return $a === [] || (array_keys($a) === range(0, count($a) - 1)); }}?>function isIndexed($array){ if (is_array($array)) { $keys = array_keys($array); return $keys === array_keys($keys); } return false;}function isAssoc($array){ if (is_array($array)) { $keys = array_keys($array); return $keys !== array_keys($keys); } return false;}these two function is more faster than divinity76+spam at gmail dot com's about three times in my computer for PHP 8.2.9:array(3) { ["pre"]=> float(0.8179779052734375) ["post"]=> float(0.8116860389709473) ["index"]=> float(0.3369460105895996)}:)old school polyfill (:<?phpif (!function_exists('array_is_list')) { function array_is_list(array $array) { if ($array === []) { return true; } $keys = array_keys($array); return $keys === array_keys($keys); }}?>