How to use subarray as value of associative array in php

During the development process, we often encounter situations where the values ​​of an associative array need to be split into multiple sub-arrays. At this time, PHP provides a very convenient method, which is to use subarrays as the values ​​of associative arrays.

So how is it implemented? Let’s analyze it step by step.

First, we need to understand what an associative array is. In PHP, an associative array is a special type of array that uses strings as keys to access array elements. For example:

$arr = array(
    'name' => '张三',
    'age' => 18,
    'gender' => '男'
);

$arr ​​above is a simple associative array. It uses strings as key names, corresponding to the corresponding values.

Next, let’s look at how to use subarrays as values ​​of associative arrays.

Suppose we have a requirement: a set of data needs to be stored according to categories, and there may be multiple sub-items under each category. In this case, we can use associative arrays.

First, we can define an associative array to store the sub-items under each category. For example:

$data = array(
    'fruit' => array(
        'apple',
        'banana',
        'orange'
    ),
    'vegetable' => array(
        'tomato',
        'carrot',
        'cucumber'
    ),
    'meat' => array(
        'beef',
        'pork',
        'chicken'
    )
);

The above $data array uses the category name as the key name, corresponding to an array containing multiple sub-items. In this way, we can easily access the sub-items under each category. For example, if you want to access the sub-items under the meat category, you can write like this:

$meat_items = $data['meat'];

At this time, $meat_items is an array containing multiple sub-items, including beef, pork and chicken.

If you need to traverse the entire $data array, you can use a foreach loop to achieve it. For example:

foreach($data as $category => $items) {
    echo '分类 '.$category.' 下的子项：'."\n";
    foreach($items as $item) {
        echo '- '.$item."\n";
    }
}

Execute the above code to print out the sub-items under each category.

Through the above analysis, we can easily find that using subarrays as values ​​of associative arrays can easily store a set of data according to categories, which facilitates subsequent operations and traversal.

To summarize, the steps to use a subarray as the value of an associative array are as follows:

1. Define an associative array to store sub-items under each category;
2. Use a subarray as the value of the associative array. The subarray contains each subitem under the category;
3. For the subitems under each category, you can use the key name of the associative array and the subscript of the subarray. access.

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