以下两个代码片段中哪个更快，为什么? [英] Which of the following two code snippets is faster, and why?

问题描述

我和 Jim O'Brien 制作了两段代码，它们的作用完全相同.但哪个更快?

I and Jim O'Brien have made two snippets of code, which do exactly the same. But which is faster?

(代码使输入数组的偶数和奇数的键值对.如果输入数组是这样的:

(The code makes key-value pairs of even and odd numbers of the input array. If the input array is this:

Array(
    "thirteen",
    13,
    "seven",
    7,
    ...
)

那么输出数组就会变成这样:

then the output array will become this:

Array(
    "thirteen" => 13,
    "seven" => 7,
    ...
)

片段 1:

<?php

$output = array();
for ($i = 0; $i < count($input); $i++) {
    $output[$input[$i]] = $input[++$i];
}

?>

代码段 2:

<?php

$output = array();
for ($i = 0; $i < count($input); $i += 2) {
    $output[$input[$i]] = $input[$i + 1];
}

?>

哪个片段更快，为什么?

Which snippet is faster, and why?

推荐答案

与预先计算 count($input) 而不是运行它会节省的相比，它们之间的区别微不足道每次循环出现时.

The difference between them is insignificant compared to what you would save if you pre-computed count($input) instead of running it every time the loop comes around.

就在您给出的两者之间，第二个更具可读性，是我会选择的一个.效率方面，根本不值得操心.

Just between the two you have given, the second is more readable and is the one I would choose. Efficiency-wise, it's just not worth bothering about.

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