How to add key name to php array

In PHP programming, array is a very important data type, which can be used to store multiple variables of different types. In the process of operating an array, we may need to add/modify the key name of the array. This article will introduce how to add keys to arrays in PHP.

1. Basic syntax

In PHP, there are two ways to add elements to an array:

1. Use square bracket syntax []

The sample code is as follows:

$array = []; // 初始化一个数组
$array['name'] = '张三';
$array['age'] = 20;

print_r($array); // 输出数组内容

In the above code, we use square brackets [] to add key names, and any number of elements can be added to the array. Use the print_r() function to output the array content. The result is as follows:

Array
(
    [name] => 张三
    [age] => 20
)

2. Use the array_push() function

The sample code is as follows:

$array = [];
array_push($array, '张三', 20);

print_r($array);

In the above code , we use the array_push() function to add elements to the array. This function will add one or more elements to the end of the array. Also use the print_r() function to output, the results are as follows:

Array
(
    [0] => 张三
    [1] => 20
)

2. Add associative array

Associative array is a special array type, and its elements use strings as key names. When adding an associative array, we need to add the key name and value to the array as a whole. The sample code is as follows:

$array = [];
$array[] = array('name'=>'张三', 'age'=>20); // 添加关联数组

print_r($array); // 输出数组内容

In the above code, we use square brackets [] to add an associative array. The key name and value need to be filled in an array(), so as to ensure the corresponding relationship between the key name and value. The output result of using the print_r() function is as follows:

Array
(
    [0] => Array
        (
            [name] => 张三
            [age] => 20
        )

)

3. Modify the key name of the array

If you want to modify the key name of the array, we can delete the original element through the unset() function, and then use Square brackets [] or the array_push() function add new elements to modify the key name. The sample code is as follows:

$array = ['name'=>'张三', 'age'=>20];

// 删除name元素
unset($array['name']);

// 添加新元素
$array['username'] = 'zhangsan';

print_r($array);

In the above code, we use the unset() function to delete the original name element, and use square brackets [] to add new elements to achieve the effect of modifying the key name. The output result of using the print_r() function is as follows:

Array
(
    [age] => 20
    [username] => zhangsan
)

4. Use foreach() to loop through the array

In actual development, it is often necessary to traverse all elements of the array. PHP provides the foreach() loop to conveniently traverse arrays. The sample code is as follows:

$array = ['name'=>'张三', 'age'=>20];

foreach ($array as $key => $value) {
    echo $key . '=>' . $value . '<br>';
}

In the above code, we use foreach() to loop through the array and output the key names and values ​​of the array in sequence. The output results are as follows:

name=>张三
age=>20

5. Summary

This article introduces several methods of adding key names to arrays in PHP, including using square brackets [], array_push() function, and adding associative arrays and modify the array key names. Additionally, we also covered how to use foreach() to loop through an array. By studying this article, I believe that readers have mastered common array operation skills and can become more proficient in using PHP for development.

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