PHP 二维数组和 foreach 循环

Question

我一直在努力解决二维数组和 foreach 循环。下面的代码展示了一个杂志数组，每个数组都指向一个一维的 Articles 数组。现在为每本杂志存储三篇文章（只是文章的标题）。我想知道如何关联一个二维数组，以便我可以存储除标题之外的作者和页码，对于属于杂志的每篇文章。你能指出我正确的方向吗？提前致谢。

<?php

// Create a magazines array
$magazines = array();

// Put 5 magazines on it
for($x=0;$x<5;$x++)
    $magazines[] = "Magazine " . $x ;

// Associate articles array to each magazine
foreach($magazines as $magazine){
    $articles[$magazine] = array();
    for($x=0;$x<3;$x++)
        $articles[$magazine][] = $magazine . " - Article Title " . $x ;
}

// List them all
foreach($magazines as $magazine){
    echo $magazine . " has these articles: <br>";
    foreach($articles[$magazine] as $article)
        echo $article . "</br>";
}
?>

Answer 1

也许你应该稍微改变一下结构：

$magazines = array();

//create magazines
for($x=0;$x<5;$x++) {
  $magazines[] = array('name' => 'Magazine ' . $x, 
                       'year' => '2011', 
                       'articles' => array());
}

//fill in some articles
foreach ($magazines as &$magazine) {
  for($x=0;$x<3;$x++) {
    $magazine['articles'][] = array('article_titel' => $magazine['name'] . " - Article Title " . $x, 
                                    'article_author' => 'author ' . $x,
                                    'article_page' => $x);
  }
}

//output
foreach($magazines as $magazine) {
  echo 'The Magazine ' . $magazine['name'] . ' from ' . $magazine['year'] . ' contains the articles : ';
  foreach($magazine['articles'] as $article) {
    echo $article['article_titel'] . ' by ' . $article['article_author'] . ' on page ' . $article['article_page'];
  }
}

一点解释： Magazines 是一个普通的数组。 然后向其中添加关联数组（杂志）。 每个magzines-array 都有一个articles-field，它是一个普通数组，您可以再次将关联数组添加到它（文章）。

所以现在，您遍历杂志，每本杂志都有一系列文章可供您迭代。

这意味着：杂志是单个杂志的数组，一个杂志是一个关联数组，它还包含一个文章数组。文章又是一个关联数组。

我希望这听起来不会太令人困惑... ;)

Answer 2

// 5 articles per magazine:
$articles = array_combine($magazines, array_fill(0, 5, array(1,2,3,4,5));

现在每本杂志有 5 篇文章，所有文章都以数字作为标题。只是为了演示。希望能帮助到你。您可以通过$articles 数组访问所有文章，然后提供杂志标题作为键。

当然，您也可以手动设置每个杂志的文章：

$articles[$magazine] = array('My first article', 'Editorial', 'Cooking with wood fire');

甚至单独：

$articles[$magazine][] = 'Learning by doing.';

编辑：如果文章提供更多内容，那么标题：

$articles[$magazine][] = array
(
  'title' => 'Learning by doing.',
  'author' => 'Frank Stein',
  'pages' => 2,
);

Answer 3

您需要将额外信息存储在杂志条目内的关联数组中：

for ( $m = 0; $m < 5; $m++ ) {
    for ( $a = 0; $a < 3; $a++ ) {
        $magazines["Magazine $m"]["Article $a"] = array(
            'title'  => "Title $a",
            'author' => "Author $a"
        );
    }
}

然后您可以通过多种方式访问​​数组中的每个元素：

// foreach loops through each element of the array,
// returning the key and value:
foreach ( $magazines as $magazine => $articles ) {
    print "$magazine\n";
    foreach ( $articles as $article => $info ) {
        print "  $article\n";
        // You can also access elements directly by their key:
        print "    Title: {$info['title']}\n";
        print "    Author: {$info['author']}\n";
    }
}

结果：

Magazine 0
  Article 0
    Title: Title 0
    Author: Author 0
  Article 1
    Title: Title 1
    Author: Author 1
  Article 2
    Title: Title 2
    Author: Author 2
Magazine 1
  Article 0
    Title: Title 0
    Author: Author 0
  ...

创建嵌套数组的方法有很多种，具体选择取决于您的要求。上面的方法只使用了关联数组，而下面的方法同时使用了关联数组和数值数组：

$magazines = array();

for ( $m = 0; $m < 5; $m++ ) {
    $magazines[$m] = array( 'title' => "Magazine $m" );
    for ( $a = 0; $a < 3; $a++ ) {
        $magazines[$m]['articles'][] = array(
            'title'  => "Article $a",
            'author' => "Author $a"
        );
    }
}

Answer 4

我不确定我是否关注这里的问题。为什么不使用以下内容？

$magazines = array(

    array( // a single magazine
        'title' => 'Issue 1',
        'articles' => array( // a list of articles
            array( // a single article
                title => 'Article 1',
                content => 'xyz'
            )
        )
    ),

);

编辑：修正小错误:)

如果你想让它以更易读的方式，你可以这样做：

function Magazines(){
    return func_get_args();
}

function Magazine($title,$articles){
    return array(
        'title' => $title,
        'articles' => $articles
    );
}

function Articles(){
    return func_get_args();
}

function Article($title,$content){
    return array(
        'title' => $title,
        'content' => $content
    );
}

// and using it...
$magazines = Magazines(Magazine('Issue 1',Articles(Article('Article 1','xyz'))));

它只是用一些好的命名替换了array()。您可以轻松地将其（或类似的）转换为 OOP。最后，OOP 只是用于管理项目。实际的存储总是一个数组。

---

遍历

一旦你有了正确的结构，读取数组实际上是非常简单的：

foreach($magazines as $magazine){
    // user things like $magazine['title'] in here...
    foreach($magazine['articles'] as $article){
        // user $article['title'] here
    }
}

这是 6 行干净的代码。

Answer 5

怎么样：

$magazines[$magazine] = array();
$magazines[$magazine]['article']['title'] = 'title';
$magazines[$magazine]['article']['other'] = 'other';

foreach ($magazines as $name => $magazine) {
    echo "name: " . $name;
    foreach ($magazine as $articleName => $article) {
        echo "title: " . $article['title'] . "\n";
        echo "other: " . $article['other'] . "\n";
    }
}