What are the characteristics of php arrays

Characteristics of php arrays: 1. Key values ​​can be any type of data, such as numbers, strings, arrays, etc.; 2. Key names can be numbers (starting from 0 by default) or strings Or a mixture of strings and numbers; 3. Array elements are represented by the name of the entire array and its subscript in the array, with the syntax "array name [subscript]"; 4. The length of the array is variable.

The operating environment of this tutorial: windows7 system, PHP8.1 version, DELL G3 computer

An array is a collection of data. Series data are organized into an actionable whole.

In PHP, an array is an ordered set of variables, where each value is called an element. Each element is distinguished by a special identifier called a key (also called a subscript).

Array is one of the most important data types in PHP and is widely used in PHP. Because PHP is a programming language with weak data types, array variables in PHP can store any number of data of any type, and can implement the functions of data structures such as heaps, stacks, and queues in other strong data types.

The purpose of using an array is to organize multiple interrelated data together to form a set and use it as a unit to achieve the purpose of batch data processing.

What are the characteristics of PHP arrays

PHP array is a very powerful and flexible data type. The following are some characteristics (features) of PHP arrays:

1. The key value can be any type of data

The key value can be a number, string, or Boolean Value, null, etc., even array type

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$arr1=array(1,2,3,"hello",null);
var_dump($arr1);
$arr2=array
(
    array("张三",25,"男"),
    array("李四",21,"男"),
);
var_dump($arr2);
?>

2. The key name can be a number or a string

In the above example, the key name of the array is a number. In fact, the key name can also be a manually set string.

PHP arrays are more flexible than arrays in other high-level languages. They not only support index arrays with numbers as keys, but also support associative arrays with strings or a mixture of strings and numbers as keys.

1) Index array--numeric key name

The subscript (key name) of the index array consists of numbers, starting from 0 by default. Each number corresponds to an array element in the array. The position does not need to be specified. PHP will automatically assign an integer value to the key name of the index array, and then automatically increase from this value. As shown below:

$arr=array(1,2,3,4,5,6,7,8,9,10);

2) Associative array--string key name

The subscript (key name) of the associative array consists of a numerical value and a string It is composed of mixed forms. If a key name in an array is not a number, then the array is an associative array. As shown below:

$arr=array("id"=>1,"name"=>"李华","age"=>23,"1"=>1,"id2"=>52);

##3. You can use loop statements to read the array in order

foreach($arr as $key => $value){
 echo $arr[$key]."<br>";
}

4. The specified element in the array can be read according to the key name (subscript)

The array element is represented by the name of the entire array and its own subscript in the array .

$arr = [1 => 'ok', 'one' => 'hello', 'a' => 'world'];
echo $arr['one'];

5. The length of the array is variable

$arr = [1, 2, 3];
$arr[] = 4;
array_push($arr, 5);

Based on these characteristics, we can use Arrays can easily implement various data structures such as sets, stacks, lists, and dictionaries.

Recommended learning: "

PHP Video Tutorial"

The above is the detailed content of What are the characteristics of php arrays. For more information, please follow other related articles on the PHP Chinese website!