如果问题，即。

$a = [
     [
       "_id" => "5a96933414d48831a41901f2",
       "discount_amount" => 3.29,
       "discount_id" => "5a92656a14d488570c2c44a2",
     ],
     [
       "_id" => "5a9790fd14d48879cf16a9e8",
       "discount_amount" => 4.53,
       "discount_id" => "5a9265b914d488548513b122",
     ],
     [
       "_id" => "5a98083614d488191304b6c3",
       "discount_amount" => 15.24,
       "discount_id" => "5a92806a14d48858ff5c2ec3",
     ],
     [
       "_id" => "5a982a4914d48824721eafe3",
       "discount_amount" => 45.74,
       "discount_id" => "5a928ce414d488609e73b443",
     ],
    [
       "_id" => "5a982a4914d48824721eafe55",
       "discount_amount" => 10.26,
       "discount_id" => "5a928ce414d488609e73b443",
     ],
   ];

岁:

function searchForId($id, $array) {
    $did=0;
    $dia=0;
   foreach ($array as $key => $val) {
       if ($val['discount_id'] === $id) {
           $dia +=$val['discount_amount'];
           $did++;
       }
   }
    if($dia != '') {
        echo $dia;
        var_dump($did);
    }
   return null;
};
print_r(searchForId('5a928ce414d488609e73b443',$a));

$a = ['x' => ['eee', 'ccc'], 'b' => ['zzz']];

$found = null;
$search = 'eee';

array_walk($a, function ($k, $v) use ($search, &$found) {
    if (in_array($search, $k)) {
        $found = $v;
    }
});

var_dump($found);

function searchForId($id, $array) {
   foreach ($array as $key => $val) {
       if ($val['uid'] === $id) {
           return $key;
       }
   }
   return null;
}

这是可行的。你应该这样称呼它:

$id = searchForId('100', $userdb);

重要的是要知道，如果你使用===运算符比较类型必须完全相同，在这个例子中，你必须搜索字符串或使用==代替===。

根据安哥拉人的回答。在PHP的后续版本(>= 5.5.0)中，可以使用一行程序。

$key = array_search('100', array_column($userdb, 'uid'));

这里是文档:http://php.net/manual/en/function.array-column.php。

看起来array_filter将是合适的解决方案…

$userdb=Array
(
    (0) => Array
        (
            (uid) => '100',
            (name) => 'Sandra Shush',
            (url) => 'urlof100'
        ),

    (1) => Array
        (
            (uid) => '5465',
            (name) => 'Stefanie Mcmohn',
            (pic_square) => 'urlof100'
        ),

    (2) => Array
        (
            (uid) => '40489',
            (name) => 'Michael',
            (pic_square) => 'urlof40489'
        )
);

PHP代码

<?php 
$search = 5465;
$found = array_filter($userdb,function($v,$k) use ($search){
  return $v['uid'] == $search;
},ARRAY_FILTER_USE_BOTH); // With latest PHP third parameter is optional.. Available Values:- ARRAY_FILTER_USE_BOTH OR ARRAY_FILTER_USE_KEY  

$values= print_r(array_values($found));
$keys =  print_r(array_keys($found)); 

我知道这个问题已经回答了，但我在代码中使用了这个问题并对其进行了扩展，这样就不需要只根据uid进行搜索了。我只是想把它分享给其他可能需要这个功能的人。

这是我的例子，请记住这是我的第一个答案。我去掉了参数数组，因为我只需要搜索一个特定的数组，但是您可以很容易地将它添加进去。我想要搜索的不仅仅是uid。

此外，在我的情况下，由于其他字段的搜索结果可能不是唯一的，可能有多个键要返回。

 /**
     * @param array multidimensional 
     * @param string value to search for, ie a specific field name like name_first
     * @param string associative key to find it in, ie field_name
     * 
     * @return array keys.
     */
     function search_revisions($dataArray, $search_value, $key_to_search) {
        // This function will search the revisions for a certain value
        // related to the associative key you are looking for.
        $keys = array();
        foreach ($dataArray as $key => $cur_value) {
            if ($cur_value[$key_to_search] == $search_value) {
                $keys[] = $key;
            }
        }
        return $keys;
    }

后来，我写了这个，以允许我搜索另一个值和关联键。因此，我的第一个示例允许您在任何特定的关联键中搜索值，并返回所有匹配的值。

第二个例子显示了在某个关联键(first_name)中找到一个值('Taylor')，在另一个关联键(hired)中找到另一个值(true)，并返回所有匹配(名字为'Taylor'并且被雇用的人的键)。

/**
 * @param array multidimensional 
 * @param string $search_value The value to search for, ie a specific 'Taylor'
 * @param string $key_to_search The associative key to find it in, ie first_name
 * @param string $other_matching_key The associative key to find in the matches for employed
 * @param string $other_matching_value The value to find in that matching associative key, ie true
 * 
 * @return array keys, ie all the people with the first name 'Taylor' that are employed.
 */
 function search_revisions($dataArray, $search_value, $key_to_search, $other_matching_value = null, $other_matching_key = null) {
    // This function will search the revisions for a certain value
    // related to the associative key you are looking for.
    $keys = array();
    foreach ($dataArray as $key => $cur_value) {
        if ($cur_value[$key_to_search] == $search_value) {
            if (isset($other_matching_key) && isset($other_matching_value)) {
                if ($cur_value[$other_matching_key] == $other_matching_value) {
                    $keys[] = $key;
                }
            } else {
                // I must keep in mind that some searches may have multiple
                // matches and others would not, so leave it open with no continues.
                $keys[] = $key;
            }
        }
    }
    return $keys;
}

函数的使用

$data = array(
    array(
        'cust_group' => 6,
        'price' => 13.21,
        'price_qty' => 5
    ),
    array(
        'cust_group' => 8,
        'price' => 15.25,
        'price_qty' => 4
    ),
    array(
        'cust_group' => 8,
        'price' => 12.75,
        'price_qty' => 10
    )
);

$findKey = search_revisions($data,'8', 'cust_group', '10', 'price_qty');
print_r($findKey);

结果

Array ( [0] => 2 ) 

在Jakub的出色回答的基础上，这里有一个更通用的搜索，将允许指定键(不仅仅是uid):

function searcharray($value, $key, $array) {
   foreach ($array as $k => $val) {
       if ($val[$key] == $value) {
           return $k;
       }
   }
   return null;
}

用法:$results = searcharray('searchvalue'， searchkey， $array);