避免多个foreach循环 [英] Avoid multiple foreach loops

问题描述

在WordPress中使用wpdb类查询数据库时，我经常得到对象的数字数组:

When querying the database using wpdb class in WordPress I often get a numerical array of objects:

array(
    [0] => stdClass(
        comment_ID = 3
        comment_post_ID = 19
        user_id = 7
    )
    [1] => stdClass(
        comment_ID = 5
        comment_post_ID = 19
        user_id = 6
    )
)

我需要使用user_id进行第二次查询.要检索user_id，我使用foreach循环，例如:

I require to perform a second query using the user_id. To retrieve the user_id I use a foreach loop like:

$user_ids = array();

foreach($array as $object) {
    $user_ids[] = $object->user_id;
}

我想知道是否有PHP本机更好的方法来检索user_id并完全避免foreach?

I want to know whether there is a PHP native better way of retrieving the user_id and avoid the foreach altogether?

推荐答案

您可以尝试使用 array_map 代替 foreach :

You may try to use array_map instead of foreach:

$user_ids = array_map(function($obj){ return $obj->user_id; }, $array);

注意::由于使用PHP 5.3 ="nofollow">匿名函数.

NOTE: This example requires at least PHP 5.3, as it was implemented with anonymous functions.

如基准测试所示，原生 foreach -循环 array_map 快.它是本机语言结构，因此效率更高.如果忽略这一事实，则只有其他循环构造(while，for)或array_map是唯一的方法.

As the benchmark shows, native foreach-loop is faster than array_map. It is more efficient, as it is a native language construction. If ignore this fact, other cycle constructions (while, for) or array_map are the only way.

但是，如果您重构查询，而无需进行php处理，那将是更好的选择.有很多功能，例如INNER JOIN，LEFT JOIN，子查询，循环和存储过程.可能真的更快.

But it would be really better, if you reconstruct your query, to execute it without php-processing. There are a lot of functionality like INNER JOIN, LEFT JOIN, subqueries, loops and stored procedures. It might be really faster.

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