好的，
我知道一切array_pop()，但这会删除最后一个元素。获取数组的最后一个元素而不删除它的最佳方法是什么？
array_pop()
编辑：这是一个奖励：
$array = array('a' => 'a', 'b' => 'b', 'c' => 'c');
甚至
$array = array('a', 'b', 'c', 'd'); unset($array[2]); echo $array[sizeof($array) - 1]; // Output: PHP Notice: Undefined offset: 2 in - on line 4
该线程中的许多答案为我们提供了许多不同的选择。为了能够从中进行选择，我需要了解他们的行为和表现。在这个答案中，我将与您分享我的发现，以 PHP 版本为基准5.6.38，7.2.10并且7.3.0RC1（预计 2018 年 12 月 13 日）。
5.6.38
7.2.10
7.3.0RC1
测试输入（<<input code>>s）与：
<<input code>>
$array = null;
$array = [];
$array = ["a","b","c",null];
$array = ["a","b","c","d"];
$array = []; $array[1] = "a"; $array[2] = "b"; $array[0] = "c";
$array = []; for($i=0;$i<100;$i++) { $array[] = $i; }
$array = []; for($i=0;$i<100000;$i++) { $array[] = $i; }
对于测试，我将使用5.6.38,7.2.10和7.3.0RC1 PHP docker 容器，例如：
sudo docker run -it --rm php:5.6.38-cli-stretch php -r '<<<CODE HERE>>>'
上面列出<<option code>>的 s 和<<input code>>s 的每个组合都将在所有版本的 PHP 上运行。对于每个测试运行，使用以下代码片段：
<<option code>>
<<input code>> error_reporting(E_ALL); <<option code>> error_reporting(0); $before=microtime(TRUE); for($i=0;$i<100;$i++){echo ".";for($j=0;$j<100;$j++){ <<option code>> }}; $after=microtime(TRUE); echo "\n"; var_dump($x); echo round(($after-$before)/(100*100)*1000*1000*1000);
对于每次运行，这将 var_dump 最后检索到的测试输入的最后一个值，并以飞秒（0.000000000000001 秒）打印一次迭代的平均持续时间。
结果如下：
/==========================================================================================================================================================================================================================================================================================================================================================================================================================\ || || T E S T I N P U T - 5 . 6 . 3 8 || T E S T I N P U T - 7 . 2 . 1 0 || T E S T I N P U T - 7 . 3 . 0 R C 1 || || || null | empty | last_null | auto_idx | shuffle | 100 | 100000 || null | empty | last_null | auto_idx | shuffle | 100 | 100000 || null | empty | last_null | auto_idx | shuffle | 100 | 100000 || ||============================OPTIONS - ERRORS==========================++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============<| || 1. $x = array_values(array_slice($array, -1))[0]; || W1 + W2 | N1 | - | - | - | - | - || W1 + W2 | N1 | - | - | - | - | - || W1 + W2 | N1 | - | - | - | - | - || || 2. $x = array_slice($array, -1)[0]; || W1 | N1 | - | - | - | - | - || W1 | N1 | - | - | - | - | - || W1 | N1 | - | - | - | - | - || || 3. $x = array_pop((array_slice($array, -1))); || W1 + W3 | - | - | - | - | - | - || W1 + N2 + W3 | N2 | N2 | N2 | N2 | N2 | N2 || W1 + N2 + W3 | N2 | N2 | N2 | N2 | N2 | N2 || || 4. $x = array_pop((array_slice($array, -1, 1))); || W1 + W3 | - | - | - | - | - | - || W1 + N2 + W3 | N2 | N2 | N2 | N2 | N2 | N2 || W1 + N2 + W3 | N2 | N2 | N2 | N2 | N2 | N2 || || 5. $x = end($array); reset($array); || W4 + W5 | - | - | - | - | - | - || W4 + W5 | N2 | N2 | N2 | N2 | N2 | N2 || W4 + W5 | - | - | - | - | - | - || || 6. $x = end((array_values($array))); || W2 + W4 | - | - | - | - | - | - || W2 + N2 + W4 | - | - | - | - | - | - || W2 + N2 + W4 | N2 | N2 | N2 | N2 | N2 | N2 || || 7. $x = $array[count($array)-1]; || - | N3 | - | - | - | - | - || W7 | N3 | - | - | - | - | - || W7 | N3 | - | - | - | - | - || || 8. $keys = array_keys($array); $x = $array[$keys[count($keys)-1]]; || W6 | N3 + N4 | - | - | - | - | - || W6 + W7 | N3 + N4 | - | - | - | - | - || W6 + W7 | N3 + N4 | - | - | - | - | - || || 9. $x = $array[] = array_pop($array); || W3 | - | - | - | - | - | - || W3 | - | - | - | - | - | - || W3 | - | - | - | - | - | - || || 10. $x = $array[array_key_last($array)]; || F1 | F1 | F1 | F1 | F1 | F1 | F1 || F2 | F2 | F2 | F2 | F2 | F2 | F2 || W8 | N4 | F2 | F2 | F2 | F2 | F2 || ||========================OPTIONS - VALUE RETRIEVED=====================++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============<| || 1. $x = array_values(array_slice($array, -1))[0]; || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || || 2. $x = array_slice($array, -1)[0]; || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || || 3. $x = array_pop((array_slice($array, -1))); || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || || 4. $x = array_pop((array_slice($array, -1, 1))); || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || || 5. $x = end($array); reset($array); || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || || 6. $x = end((array_values($array))); || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || || 7. $x = $array[count($array)-1]; || NULL | NULL | NULL | string(1) "d" | string(1) "b" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "b" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "b" | int(99) | int(99999) || || 8. $keys = array_keys($array); $x = $array[$keys[count($keys)-1]]; || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || || 9. $x = $array[] = array_pop($array); || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || || 10. $x = $array[array_key_last($array)]; || N/A | N/A | N/A | N/A | N/A | N/A | N/A || N/A | N/A | N/A | N/A | N/A | N/A | N/A || N/A | N/A | N/A | N/A | N/A | N/A | N/A || ||=================OPTIONS - FEMTOSECONDS PER ITERATION=================++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============<| || 1. $x = array_values(array_slice($array, -1))[0]; || 803 | 466 | 390 | 384 | 373 | 764 | 1.046.642 || 691 | 252 | 101 | 128 | 93 | 170 | 89.028 || 695 | 235 | 90 | 97 | 95 | 188 | 87.991 || || 2. $x = array_slice($array, -1)[0]; || 414 | 349 | 252 | 248 | 246 | 604 | 1.038.074 || 373 | 249 | 85 | 91 | 90 | 164 | 90.750 || 367 | 224 | 78 | 85 | 80 | 155 | 86.141 || || 3. $x = array_pop((array_slice($array, -1))); || 724 | 228 | 323 | 318 | 350 | 673 | 1.042.263 || 988 | 285 | 309 | 317 | 331 | 401 | 88.363 || 877 | 266 | 298 | 300 | 326 | 403 | 87.279 || || 4. $x = array_pop((array_slice($array, -1, 1))); || 734 | 266 | 358 | 356 | 349 | 699 | 1.050.101 || 887 | 288 | 316 | 322 | 314 | 408 | 88.402 || 935 | 268 | 335 | 315 | 313 | 403 | 86.445 || || 5. $x = end($array); reset($array); || 715 | 186 | 185 | 180 | 176 | 185 | 172 || 674 | 73 | 69 | 70 | 66 | 65 | 70 || 693 | 65 | 85 | 74 | 68 | 70 | 69 || || 6. $x = end((array_values($array))); || 877 | 205 | 320 | 337 | 304 | 2.901 | 7.921.860 || 948 | 300 | 336 | 308 | 309 | 509 | 29.696.951 || 946 | 262 | 301 | 309 | 302 | 499 | 29.234.928 || || 7. $x = $array[count($array)-1]; || 123 | 300 | 137 | 139 | 143 | 140 | 144 || 312 | 218 | 48 | 53 | 45 | 47 | 51 || 296 | 217 | 46 | 44 | 53 | 53 | 55 || || 8. $keys = array_keys($array); $x = $array[$keys[count($keys)-1]]; || 494 | 593 | 418 | 435 | 399 | 3.873 | 12.199.450 || 665 | 407 | 103 | 109 | 114 | 431 | 30.053.730 || 647 | 445 | 91 | 95 | 96 | 419 | 30.718.586 || || 9. $x = $array[] = array_pop($array); || 186 | 178 | 175 | 188 | 180 | 181 | 186 || 83 | 78 | 75 | 71 | 74 | 69 | 83 || 71 | 64 | 70 | 64 | 68 | 69 | 81 || || 10. $x = $array[array_key_last($array)]; || N/A | N/A | N/A | N/A | N/A | N/A | N/A || N/A | N/A | N/A | N/A | N/A | N/A | N/A || 370 | 223 | 49 | 52 | 61 | 57 | 52 || \=========================================================================================================================================================================================================================================================================================================================================================================================================================/
上面提到的 致命 、 警告 和 注意 代码翻译为：
F1 = Fatal error: Call to undefined function array_key_last() in Command line code on line 1 F2 = Fatal error: Uncaught Error: Call to undefined function array_key_last() in Command line code:1 W1 = Warning: array_slice() expects parameter 1 to be array, null given in Command line code on line 1 W2 = Warning: array_values() expects parameter 1 to be array, null given in Command line code on line 1 W3 = Warning: array_pop() expects parameter 1 to be array, null given in Command line code on line 1 W4 = Warning: end() expects parameter 1 to be array, null given in Command line code on line 1 W5 = Warning: reset() expects parameter 1 to be array, null given in Command line code on line 1 W6 = Warning: array_keys() expects parameter 1 to be array, null given in Command line code on line 1 W7 = Warning: count(): Parameter must be an array or an object that implements Countable in Command line code on line 1 W8 = Warning: array_key_last() expects parameter 1 to be array, null given in Command line code on line 1 N1 = Notice: Undefined offset: 0 in Command line code on line 1 N2 = Notice: Only variables should be passed by reference in Command line code on line 1 N3 = Notice: Undefined offset: -1 in Command line code on line 1 N4 = Notice: Undefined index: in Command line code on line 1
基于此输出，我得出以下结论：
$x = end((array_values($array)));
$keys = array_keys($array); $x = $array[$keys[count($keys)-1]];
$x = end($array); reset($array);
$x = $array[count($array)-1];
$x = $array[] = array_pop($array);
$x = $array[array_key_last($array)];
count
array_key_last
取决于将数组用作堆栈还是队列，您可以对选项 9 进行更改。
