为什么简单的PHP数组查找如此之慢？我在这里做错了吗？

Question

我有以下功能:

function percentToColor($percent){
    $minBrightness = 160;
    $maxBrightness = 255;

    // Remainins?
    $brightness = ((($minBrightness-$maxBrightness)/(100-0))*$percent+$maxBrightness);
    $first = (1-($percent/100))*$brightness;
    $second = ($percent/100)*$brightness;

    // Find the influence of the middle color (yellow if 1st and 2nd are red and green)
    $diff = abs($first-$second);
    $influence = ($brightness-$diff)/2;
    $first = intval($first + $influence);
    $second = intval($second + $influence);

    // Convert to HEX, format and return
    $firstHex = str_pad(dechex($first),2,0,STR_PAD_LEFT);
    $secondHex = str_pad(dechex($second),2,0,STR_PAD_LEFT);

    return $firstHex . $secondHex . '00';
}

此函数接受0到100之间的整数,并返回该数字的颜色信息.想象一个进度条,红色为0,绿色为100.这就是函数的作用.

所以我明白了:如果这个函数总是为每个输入返回相同的颜色(即颜色不依赖于时间/用户/会话),最好的想法是用结果创建一个PHP数组,对吗？

所以我重写了这个函数:

function percentToColorNew($percent){
   $results = array(
      0 => 'ff0000',
      1 => 'fe0500',
      2 => 'fd0a00',
      3 => 'fc0f00',
      // ... continues with 4, 5, up until 100 ...
      99 => '03a000',
      100 => '00a000'
   );
   return $results[$percent];
}

我测试它.而意外的事情发生了!新函数只返回结果数组的结果,所需的时间是原始函数的两倍,每次调用时都必须计算结果.

为什么是这样？PHP数组这么慢吗？是否有更快的方法来存储功能结果以加速功能？可能是一个开关？如果/ elseif/else条件？使用数组的另一种方式？

Answer 1

这很慢,因为每次调用函数时都要初始化数组.

在函数之外设置数组,它应该快得多.快速而肮脏的例子:

$results = array(
    0 => 'ff0000',
    1 => 'fe0500',
    2 => 'fd0a00',
    3 => 'fc0f00',
    // ... continues with 4, 5, up until 100 ...
    99 => '03a000',
    100 => '00a000'
);

function percentToColorNew($percent){
    global $results;
    return $results[$percent];
}

编辑:或者甚至更好地使用static关键字:

function percentToColorNew($percent){
    static $results;
    if(!is_array($results)) {
        $results = array ( ... );
    }
    return $results[$percent];
}