如何在php中的多维数组中进行foreach循环

Question

我是 php 新手，想了解 foreach 循环。抱歉，如果这是一个题外话，并且之前已经讨论过，但我从其他帖子中找不到什么帮助。

下面是两个不同的数组以及用于获取键值的循环（第一个称为 $size 非常简单，我对此没有任何问题；第二个称为 $size2 循环遍历数组，但我看到错误浏览器中的消息 - 请建议我做错了什么）：

one level array:
$size = array(
    "day" => "friday",
    "place" => "office",
    "task" => "smalot",
);

foreach loop to fetch our key-values from $size (it works fine):

foreach ($size as $key => $value) {
    echo $key . "=>" . $value . "";
}

two level array:

$size2 = array(
    "day" => "friday",
    "place" => "office",
    "task" => "smalot",
    "level2" => array(
        "place" => "desk",
        "laptop" => "lenovo",
        "coffee" => "black",
    )
);

foreach loop to fetch our key-values from $size2 (it works not properly):

foreach ($size2 as $key => $value) {
    echo $key . "=>" . $value . "<br>";
    
    foreach ($value as $subkey => $subvalue) {
        echo $subkey . "=>" . $subvalue . "<br>";
        }
}

$size2 的 foreach 循环结果如下：

day=>friday

Warning: foreach() argument must be of type array|object, string given in C:\xampp\htdocs\pdfparser\size.php on line 35
place=>office

Warning: foreach() argument must be of type array|object, string given in C:\xampp\htdocs\pdfparser\size.php on line 35
task=>smalot

Warning: foreach() argument must be of type array|object, string given in C:\xampp\htdocs\pdfparser\size.php on line 35

Warning: Array to string conversion in C:\xampp\htdocs\pdfparser\size.php on line 33
level2=>Array
place=>desk
laptop=>lenovo
coffee=>black

如果我取消注释内部循环，那么我可以从上部数组中获取键值：

foreach ($size2 as $key => $value) {
    echo $key . "=>" . $value . "<br>";
    
//   foreach ($value as $subkey => $subvalue) {
//        echo $subkey . "=>" . $subvalue . "<br>";
//    }
}

result:
day=>friday
place=>office
task=>smalot

Warning: Array to string conversion in C:\xampp\htdocs\pdfparser\size.php on line 33
level2=>Array

但目标是从数组中获取上部和内部键值并且看不到错误消息。我该怎么办？再次感谢！

-

Answer 1

问题是，并非

$size2

数组中的每个元素本身都是数组。当您的 foreach 循环尝试将 '

friday

'、'

office

' 和 '

smalot

' 视为数组以便循环遍历它们时，它会抛出错误，因为它们是 strings，而不是 arrays。

您需要在 foreach 循环中添加一个检查，以查看该值是否是一个数组，然后再尝试循环它。

$size2 = array(
    "day" => "friday",
    "place" => "office",
    "task" => "smalot",
    "level2" => array(
        "place" => "desk",
        "laptop" => "lenovo",
        "coffee" => "black",
    )
);

foreach ($size2 as $key => $value) {
    if (is_array($value)) {
        echo $key . " has an inner array:<br>";
        foreach ($value as $subkey => $subvalue) {
            echo $subkey . " => " . $subvalue . "<br>";
        }
    } else {
        echo $key . " => " . $value . "<br>";
    }
}

如果它确实是一个数组，则只会循环遍历

$value

。