在 PHP 中迭代数组的最快方法 [英] Fastest way to iterate array in PHP

问题描述

我正在学习 Zend PHP 认证.

I'm studying for the Zend PHP certification.

不确定这个问题的答案.

Not sure the answer to this question.

问题:使用 PHP 5 迭代和修改数组的每个元素的最佳方法是什么?

a) 您不能在迭代期间修改数组

a) You cannot modify an array during iteration

b) for($i = 0; $i

c) foreach($array as $key => &$val) {/* ... */}

d) foreach($array as $key => $val) {/* ... */}

e) while(list($key, $val) = each($array)) {/* ... */}

<小时>

我的直觉是 (B) 因为不需要创建临时变量然后我意识到它不适用于关联数组.在网上进一步搜索发现:将不变数组计数存储在单独的变量中可提高性能.

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My instinctive is (B) since there is no need to create temporary variable then I realize it won't work for associative arrays. Further searching around the net found this: Storing the invariant array count in a separate variable improves performance.

$cnt = count($array);
for ($i = 0; $i < $cnt; $i++) { }

推荐答案

从这些选项来看，C 将是显而易见的答案.

From these options C would be the obvious answer.

其余选项(除 A 外) 可用于实现这一点，具体取决于括号内的代码，但问题并未显示该代码.所以一定是C.

The remaining options (besides A) may be used to achieve that, depending on the code inside the parenthesis, but the question does NOT show that code. So it must be C.

并且您回答了错误的问题 - 在 for 循环之前执行 count() 会提高性能，但这个问题与性能无关.

And you are answering the wrong question - yes doing count() before the for cycle will improve performance, but this question is not about performance.

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