How to assign key values ​​to php array

In PHP, array is a very important data structure and is often used to store and operate large amounts of data. The key value of an array is very important, it determines the uniqueness and access method of an array. In this article, we will discuss how to set key values ​​for PHP arrays.

First, let us understand the basic structure of PHP arrays. PHP arrays can be defined in two ways: indexed arrays and associative arrays. Indexed arrays are the most common array type, each element of which has a numeric key value and can also be accessed through numeric indexes. Associative arrays define some special key names, which can be strings or numbers.

For an associative array, we can set the key value in the following way:

$array = array(
    "name" => "Tom",
    "age" => 30,
    "gender" => "male"
);

The above code defines an associative array containing three elements, each element has its own key name and key value. In this example, we use strings as key names to identify each element, and assign the corresponding key values ​​to "Tom", "30" and "male" respectively.

The key names of associative arrays can be very flexible and can be strings, numbers, or any other data type. The following is another example of an associative array, where the keys are numbers:

$array = array(
    0 => "apple",
    1 => "banana",
    2 => "orange"
);

This array contains three elements, their key names are 0, 1, and 2, and the corresponding key values ​​are It's "apple", "banana" and "orange".

In addition to associative arrays, PHP also supports indexed arrays. For indexed arrays, we can use the following method to assign values:

$array = array("apple", "banana", "orange");

In this example, we do not need to explicitly specify the key name, but directly write the value of each element in the array. In this case, PHP uses integers such as 0, 1, 2, and 3 as key names by default.

It is worth noting that PHP also supports mixed arrays, that is, arrays that contain both numeric indexes and string key names. For mixed arrays, we can assign values ​​in the following way:

$array = array(
    "name" => "Tom",
    "age" => 30,
    0 => "apple",
    1 => "banana",
    2 => "orange"
);

In mixed arrays, we can use any data type as a key name to identify elements. At the same time, we can also access elements in the array through numerical indexes, such as:

echo $array[0];

Finally, it should be noted that in PHP, we can add, modify and delete array elements in the following ways Key value:

//新增数组元素
$array["address"] = "Beijing";

//修改数组元素
$array["age"] = 40;

//删除数组元素
unset($array["name"]);

In short, in PHP, the key value of an array can be any data type. It is very flexible and easy to operate during the definition, access and modification of the array. For more advanced operations on PHP arrays, you can refer to PHP official documentation and related books.

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