PHP'；s范围('；A'；，'；Z'；）返回一个静态数组

我忽略了一些代码，这些代码是我为在产品页面上生成A-Z导航而编写的，而执行此操作的方法是for循环；使用CCD_ 1 65-91和PHP的CCD_。我想知道是否有一种更简单和/或更有效的方法可以做到这一点，我发现PHP的range()函数支持字母范围。

在我写了测试代码来比较不同的方法后，我想到了几个问题：

1. PHP是否存储字母表的静态数组
2. 我如何才能更深入地分析PHP层下面的内容发生了什么事

我有一个PHP脚本的缓存，如果需要，除了环境配置之外，还可以附加它。对于那些可能想知道执行它的机器规格的人来说，这里有一些链接：

root@workbox：~$lshwhttp://pastebin.com/cZZRjJcR

root@workbox：~$系统信息http://pastebin.com/ihQkkPAJ

<?php
/*
 * determine which method out of 3 for returning
 * an array of uppercase alphabetic characters 
 * has the highest performance
 * 
 * +++++++++++++++++++++++++++++++++++++++++++++
 * 
 * 1) Array $alpha = for($x = 65; $x < 91; $x++) { $upperChr[] = chr($x); }
 * 2) Array $alpha = range(chr(65), chr(90);
 * 3) Array $alpha = range('A', 'Z');
 * 
 * +++++++++++++++++++++++++++++++++++++++++++++
 * 
 * test runs with iterations:
 * 
 * 10,000:
 * - 1) upperChrElapsed: 0.453785s
 * - 2) upperRangeChrElapsed: 0.069262s
 * - 3) upperRangeAZElapsed: 0.046110s
 * 
 * 100,000:
 * - 1) upperChrElapsed: 0.729015s
 * - 2) upperRangeChrElapsed: 0.078652s
 * - 3) upperRangeAZElapsed: 0.052071s
 * 
 * 1,000,000:
 * - 1) upperChrElapsed: 50.942950s
 * - 2) upperRangeChrElapsed: 10.091785s
 * - 3) upperRangeAZElapsed: 8.073058s
 */
ini_set('max_execution_time', 0);
ini_set('memory_limit', 0);
define('ITERATIONS', 1000000); // 1m loops x3
$upperChrStart = microtime(true);
for($i = 0; $i <= ITERATIONS; $i++) {
    $upperChr = array();
    for($x = 65; $x < 91; $x++) {
            $upperChr[] = chr($x);
    }
}
$upperChrElapsed = microtime(true) - $upperChrStart;
// +++++++++++++++++++++++++++++++++++++++++++++
$upperRangeChrStart = microtime(true);
for($i = 0; $i <= ITERATIONS; $i++) {
    $upperRangeChr = range(chr(65), chr(90));   
}
$upperRangeChrElapsed = microtime(true) - $upperRangeChrStart;
// +++++++++++++++++++++++++++++++++++++++++++++
$upperRangeAZStart = microtime(true);
for($i = 0; $i <= ITERATIONS; $i++) {
    $upperRangeAZ = range('A', 'Z');    
}
$upperRangeAZElapsed = microtime(true) - $upperRangeAZStart;
printf("upperChrElapsed: %f'n", $upperChrElapsed);
printf("upperRangeChrElapsed: %f'n", $upperRangeChrElapsed);
printf("upperRangeAZElapsed: %f'n", $upperRangeAZElapsed);
?>