A guide to JSON parsing and generation in PHP

With the continuous development and application of Internet technology, front-end and back-end data interaction has become a necessary part of Web development. As a lightweight data exchange format, JSON has become one of the most popular choices. As an important language in the field of web development, PHP also provides a complete JSON processing function library, so developers can easily parse and generate JSON data. This article will introduce how to parse and generate JSON in PHP.

1. Basic concepts of JSON

JSON (JavaScript Object Notation) is a lightweight data exchange format that describes the data structure in a concise textual manner. JSON uses key-value pairs to represent data and supports basic data types, arrays, objects and other data structures. Its syntax is very similar to JavaScript object literals because JSON is derived from JavaScript object literals.

The following is a simple JSON example:

{
    "name": "Jack",
    "age": 22,
    "address": {
        "province": "Guangdong",
        "city": "Shenzhen"
    },
    "hobby": ["reading", "music"]
}

The above example contains an object that contains four key-value pairs. Among them, name and age are basic data types, address is an object, and hobby is an array. As you can see, the format of JSON data is very concise and clear.

2. Parse JSON data

PHP provides the json_decode() function to parse JSON data. The parameter of this function is a string in JSON format, and the return value is an object or array. If parsing fails, NULL is returned.

The following is the basic usage of the json_decode() function:

$jsonStr = '{"name":"Jack","age":22}';
$jsonObj = json_decode($jsonStr);
echo $jsonObj->name; // 输出 Jack
echo $jsonObj->age; // 输出 22

In the above example, a JSON format string is first defined$jsonStr, which represents an object containing key-value pairs of name and age. Next, use the json_decode() function to parse $jsonStr into an object $jsonObj. Finally, the values ​​of name and age are accessed through the $jsonObj object and output.

When the JSON data contains arrays or deeper nested structures, the json_decode() function can automatically parse it into a multi-dimensional array. The following is a JSON example containing arrays and objects:

$jsonStr = '{
  "name": "Jack",
  "friends": [
    {
      "name": "Tom",
      "age": 22
    }, 
    {
      "name": "Jerry",
      "age": 23
    }
  ]
}';
$jsonArr = json_decode($jsonStr, true);
echo $jsonArr['friends'][0]['name']; // 输出 Tom

In the above example, since the second parameter is set to true, json_decode() returns Is an associative array rather than an object. The data in $jsonArr can be accessed through multi-dimensional array indexing.

3. Generate JSON data

PHP also provides the json_encode() function to convert an object or array into a JSON string, which can be used directly Front-end and back-end data interaction.

The following is the basic usage of the json_encode() function:

$data = [
  'name' => 'Tom',
  'age' => 22
];
echo json_encode($data); // 输出 {"name":"Tom","age":22}

In the above example, first define a function containing name and age An associative array of two key-value pairs$data. Next, use the json_encode() function to convert $data into a JSON string and output it.

It should be noted that when PHP objects and arrays are converted into JSON strings, Chinese will be escaped into Unicode encoding by default. You can avoid Chinese escaping by setting the JSON_UNESCAPED_UNICODE constant. At the same time, you can also set the indentation and space symbols of the output format.

The following are common optional parameters of the json_encode() function:

• JSON_PRETTY_PRINT Make the output format indented and make writing more friendly .
• JSON_UNESCAPED_UNICODE Do not escape Chinese characters.
• JSON_UNESCAPED_SLASHES Do not escape slashes.
• JSON_NUMERIC_CHECK Convert string numbers to numeric types.
• JSON_FORCE_OBJECT Convert the array to object output, ensuring that the returned object must be in object form.

The above parameters can be used in combination, for example:

$data = [
  'name' => 'Tom',
  'age' => 22
];
echo json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);

In the above example, the two parameters JSON_PRETTY_PRINT and JSON_UNESCAPED_UNICODE Used in combination, the output format is indented and does not escape Chinese.

4. Summary

In PHP, using JSON format for data interaction has become one of the most common practices. This article starts from the concept of JSON and introduces the method of parsing and generating JSON in PHP. Developers can choose the appropriate method to implement JSON operations based on actual needs. Understanding the relevant knowledge of JSON will help us better interact with front-end and back-end data and improve the development efficiency of web applications.

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