将数组/对象树的键转换为小写 [英] Converting keys of an array/object-tree to lowercase

问题描述

我目前正在优化一个 PHP 应用程序，发现一个函数被调用了大约 10-20k 次，所以我想我会从那里开始优化:

I am currently optimizing a PHP application and found one function being called around 10-20k times, so I'd thought I'd start optimization there:

function keysToLower($obj)
{
        if(!is_object($obj) && !is_array($obj)) return $obj;
        foreach($obj as $key=>$element)
        {
                $element=keysToLower($element);
                if(is_object($obj))
                {
                        $obj->{strtolower($key)}=$element;
                        if(!ctype_lower($key)) unset($obj->{$key});
                }
                else if(is_array($obj) && ctype_upper($key))
                {
                        $obj[strtolower($key)]=$element;
                        unset($obj[$key]);
                }
        }
        return $obj;
}

大部分时间都花在递归调用上(在 PHP 中这很慢)，但我没有看到任何将其转换为循环的方法.你会怎么做?

Most of the time is spent in recursive calls (which are quite slow in PHP), but I don't see any way to convert it to a loop. What would you do?

这个版本没有考虑关联数组，因为我的数据没有，但比原始版本快了近 10 倍.大部分工作由 Gumbo 完成，主要的加速来自使用引用和创建新对象，而不是取消设置旧键.

This version doesn't account for associative arrays since my data doesn't have any, but is nearly 10 times faster than the original version. Most of the work was done by Gumbo, the major speedup comes from using references and creating a new object instead of unsetting the old keys.

function &keysToLower(&$obj)
{
    if(is_object($obj))
    {
        $newobj = (object) array();
        foreach ($obj as $key => &$val)
            $newobj->{strtolower($key)} = keysToLower($val);
        $obj=$newobj;
    }
    else if(is_array($obj))
        foreach($obj as &$value)
            keysToLower($value);
    return $obj;
}

推荐答案

Foreach 正在使用内部副本，然后遍历该副本.不尝试:

Foreach is using an internal copy that is then traversed. Try it without:

function keysToLower($obj)
{
    $type = (int) is_object($obj) - (int) is_array($obj);
    if ($type === 0) return $obj;
    reset($obj);
    while (($key = key($obj)) !== null)
    {
        $element = keysToLower(current($obj));
        switch ($type)
        {
        case 1:
            if (!is_int($key) && $key !== ($keyLowercase = strtolower($key)))
            {
                unset($obj->{$key});
                $key = $keyLowercase;
            }
            $obj->{$key} = $element;
            break;
        case -1:
            if (!is_int($key) && $key !== ($keyLowercase = strtolower($key)))
            {
                unset($obj[$key]);
                $key = $keyLowercase;
            }
            $obj[$key] = $element;
            break;
        }
        next($obj);
    }
    return $obj;
}

或者使用引用来避免使用副本:

Or use references to avoid that a copy is used:

function &keysToLower(&$obj)
{
    $type = (int) is_object($obj) - (int) is_array($obj);
    if ($type === 0) return $obj;
    foreach ($obj as $key => &$val)
    {
        $element = keysToLower($val);
        switch ($type)
        {
        case 1:
            if (!is_int($key) && $key !== ($keyLowercase = strtolower($key)))
            {
                unset($obj->{$key});
                $key = $keyLowercase;
            }
            $obj->{$key} = $element;
            break;
        case -1:
            if (!is_int($key) && $key !== ($keyLowercase = strtolower($key)))
            {
                unset($obj[$key]);
                $key = $keyLowercase;
            }
            $obj[$key] = $element;
            break;
        }
    }
    return $obj;
}

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