Contents: Introduction to XML, Parsing and Usage of JSON, Differences Between XML and JSON
1. XML
XML, or Extensible Markup Language, is a markup language in which tags are user-defined, such as <person></person>
.
Specifications:
- The first line must be a document declaration.
- There must be a root element.
- No spaces, numbers, or dots are allowed at the beginning of tag names, and it is case-sensitive.
- Nesting cannot cross boundaries.
- Attribute values must be enclosed in double quotes (browsers automatically correct to double quotes).
- Special symbols must be represented using entities.
- Comments are similar to HTML.
Although XML can be used to describe and transmit complex data, its parsing is complex, and the file size tends to be large. Therefore, it is rarely used in practical development.
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Differences Between XML and HTML
- XML is an extensible markup language, while HTML is a hypertext markup language.
- XML tags are user-defined, while HTML tags follow W3C specifications and must adhere to those standards.
- XML is primarily used for software configuration files and data transmission, often requiring custom parsing.
- HTML is used for displaying web content and is parsed by web browsers.
2. JSON
JSON, which stands for JavaScript Object Notation, is another lightweight text-based data interchange format that is language-independent.
When interacting between clients and servers, minimizing the number of interactions for performance reasons is important, and caching is often used to reduce data transfer.
- Data is stored in name/value pairs.
- Data is separated by commas (the last key/value pair must not have a trailing comma).
- Objects are enclosed in curly braces, and arrays are enclosed in square brackets.
- Double quotes are used for property names and string values.
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JSON data is transmitted as strings in different programming languages, each with its own parsing methods. The data needs to be parsed to be accessed.
2.1 PHP Parsing Methods
json_encode() and json_decode().
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2.2 JavaScript Parsing Methods
Converting JSON objects:
Method | Description |
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eval(); | Converts a string to JSON (provided by browsers). |
JSON.parse(); | Converts a string to JSON (JavaScript API with some compatibility issues). |
JSON.stringify(); | Converts JSON to a string. |
In summary, JSON is lightweight, easy to parse, and efficient, making it the preferred choice in practical development.
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