如何找到关联数组的第一/第二元素时关键是未知？ [英] How to find first/second element of associative array when keys are unknown?

问题描述

在PHP中，当你有一个关联数组，例如：

  $组['段落'] = 3
$组['行'] = 3
 

什么是访问数组的第一个或第二个元素，当你不知道该键的值的语法

有没有在C＃LINQ声明类似，你可以说：

  $ mostFrequentGroup = $组 - ＆gt;首先（）？
 

或

  $ mostFrequentGroup = $组 - ＆GT; getElementWithIndex（0）？
 

或者我必须使用foreach语句，并挑选出来，因为我在这个code例如底部做的：

  //应该返回段落
回声getMostFrequentlyOccurringItem（阵列（'行'，'段落'，'段落'））;//应该返回线
回声getMostFrequentlyOccurringItem（阵列（'wholeNumber，日期，日期，行，行，行））;//应该返回null
回声getMostFrequentlyOccurringItem（阵列（'wholeNumber'，'wholeNumber'，'段'，'段'））;//应该返回wholeNumber
回声getMostFrequentlyOccurringItem（阵列（'wholeNumber'，''，''，''））;功能getMostFrequentlyOccurringItem（$项目）{    //抓无效项
    如果（$项目== NULL）{
        返回null;
    }
    如果（计数（$项目）== 0）{
        返回null;
    }    //分类
    $组= array_count_values​​（$项目）;
    arsort（$组）;    //如果有一条领带，然后返回null
    如果（$组[0] == $组[1]）{// ********如何做到这一点？ ***********
        返回null;
    }    //获取最常见
    $ mostFrequentGroup ='';
    的foreach（$群体为$组=＆GT; $ numberOfTimesOccurrred）{
        如果（修剪（$组）！=''）{
            $ mostFrequentGroup = $组;
            打破;
        }
    }
    返回$ mostFrequentGroup;
}
 

解决方案

使用这些函数来设置内部数组指针：

<一个href=\"http://ch.php.net/manual/en/function.reset.php\">http://ch.php.net/manual/en/function.reset.php

<一个href=\"http://ch.php.net/manual/en/function.end.php\">http://ch.php.net/manual/en/function.end.php

而这其中，以获得实际的元素：
<一href=\"http://ch.php.net/manual/en/function.current.php\">http://ch.php.net/manual/en/function.current.php

 复位（$组）;
回声电流（$组）; //第一个
端（$组）;
回声电流（$组）; //最后一个
 

如果你想有最后/第一的键的然后就做类似 $ TMP = array_keys（$组）;

In PHP when you have an associative array, e.g.:

$groups['paragraph'] = 3
$groups['line'] = 3

what is the syntax to access the first or second element of the array when you don't know the value of the keys?

Is there something like in a C# LINQ statement where you can say:

$mostFrequentGroup = $groups->first()?

or

$mostFrequentGroup = $groups->getElementWithIndex(0)?

Or do I have to use a foreach statement and pick them out as I do at the bottom of this code example:

//should return "paragraph"
echo getMostFrequentlyOccurringItem(array('line', 'paragraph', 'paragraph'));

//should return "line"
echo getMostFrequentlyOccurringItem(array('wholeNumber', 'date', 'date', 'line', 'line', 'line'));

//should return null
echo getMostFrequentlyOccurringItem(array('wholeNumber', 'wholeNumber', 'paragraph', 'paragraph'));

//should return "wholeNumber"
echo getMostFrequentlyOccurringItem(array('wholeNumber', '', '', ''));

function getMostFrequentlyOccurringItem($items) {

    //catch invalid entry
    if($items == null) {
        return null;
    }
    if(count($items) == 0) {
        return null;
    }

    //sort
    $groups = array_count_values($items);
    arsort($groups);

    //if there was a tie, then return null
    if($groups[0] == $groups[1]) { //******** HOW TO DO THIS? ***********
        return null;
    }

    //get most frequent
    $mostFrequentGroup = '';
    foreach($groups as $group => $numberOfTimesOccurrred) {
        if(trim($group) != '') {
            $mostFrequentGroup = $group;
            break;
        }
    }
    return $mostFrequentGroup;
}

解决方案

use these functions to set the internal array pointer:

http://ch.php.net/manual/en/function.reset.php

http://ch.php.net/manual/en/function.end.php

And this one to get the actual element: http://ch.php.net/manual/en/function.current.php

reset($groups);
echo current($groups); //the first one
end($groups);
echo current($groups); //the last one

If you wanna have the last/first key then just do something like $tmp = array_keys($groups); .

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