A brief analysis of the characteristics and differences between JSON arrays and objects in PHP

JSON is a common data transfer format that is frequently used in web development. PHP also provides related functions and libraries to process JSON. In PHP, JSON can be represented as an object or an array. This article will focus on the characteristics and differences of JSON arrays and objects.

1. JSON Introduction

JSON (JavaScript Object Notation) is a lightweight data exchange format that is easy to read and write, and easy for machines to parse and generate. JSON consists of two structures: key-value pairs and arrays. In PHP, the json_encode() function can be used to convert arrays or objects into JSON data format; the json_decode() function can be used to decode JSON data into PHP arrays or objects.

2. JSON array

JSON array is an ordered collection, that is, a list containing multiple elements. Each element can be a number, string, or Boolean , null and other arrays or objects. In PHP, create a JSON array through array notation, for example:

$students = [
    "Tom",
    "Mary",
    "Jack"
];
$json = json_encode($students);
echo $json; // ["Tom","Mary","Jack"]

JSON array is marked by square brackets "[]", and each element is separated by commas. In PHP, the JSON array is decoded and converted into a PHP array through the json_decode() function, for example:

$students = '["Tom","Mary","Jack"]';
$arr = json_decode($students);
var_dump($arr); //array(3) { [0]=> string(3) "Tom" [1]=> string(4) "Mary" [2]=> string(4) "Jack" }

As you can see, the decoded PHP array has the same structure as the original array, and each element is marked with the corresponding subscript form storage.

3. JSON Object

JSON object is an unordered collection, that is, a form composed of "key-value" pairs, with each key-value pair separated by Comma separated. In PHP, JSON objects are created through associative array notation, for example:

$student = [
    "name" => "Tom",
    "age" => 18,
    "score" => 85.5
];
$json = json_encode($student);
echo $json; // {"name":"Tom","age":18,"score":85.5}

The JSON object is marked by curly brackets "{}", and each key-value pair is represented in the corresponding "key:value" form. In PHP, the JSON object is decoded and converted into a PHP object through the json_decode() function, for example:

$student = '{"name":"Tom","age":18,"score":85.5}';
$obj = json_decode($student);
var_dump($obj); //object(stdClass)#1 (3) { ["name"]=> string(3) "Tom" ["age"]=> int(18) ["score"]=> float(85.5) }

As you can see, the decoded PHP object uses "->" to access properties and associative array access The way is different. In addition, if you need to decode the JSON object into a PHP associative array, you can set the second parameter to true, for example:

$student = '{"name":"Tom","age":18,"score":85.5}';
$arr = json_decode($student, true);
var_dump($arr); //array(3) { ["name"]=> string(3) "Tom" ["age"]=> int(18) ["score"]=> float(85.5) }

You can see that the decoded PHP array has the same form as the associative array, and each key-value pair Stored in the form of corresponding "key => value".

4. The difference between JSON arrays and objects

JSON arrays and objects are structurally different. The specific differences are as follows:

(1) Arrays are It is composed of an ordered set. Each element can be a number, string, Boolean, null and other array or object; and the object is composed of "key-value" pairs, and each key-value pair is arranged in an unordered manner. The key must be of string type, and the value can be a number, string, Boolean, null, array, object, etc.

(2) Arrays are represented by square brackets "[]", and each element is separated by commas; while objects are represented by curly brackets "{}", and each key-value pair is also separated by commas.

(3) In PHP, JSON arrays are created through array notation, JSON objects are created through associative array notation, and JSON data can be decoded into PHP arrays or objects through the json_decode() function.

In short, JSON arrays and objects are common data formats, which can be converted and processed in PHP through corresponding functions and class libraries. In applications, selecting and using different data formats according to actual needs can better meet various needs.

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