PHP and XML technical analysis

What is XML? XML (eXensible Markup Language), extensible markup language, is a language used to describe other languages, which allows users to design their own standards.

Four features:

Ease of use, structure, openness, and separation.

Structural: A language with a hierarchical structure, including multiple levels of nesting.

(2) XML syntax

Document structure: declaration, processing instructions, comments, elements. Element consists of tags, attributes, etc.

Namespaces can be used to ensure the uniqueness of elements and attributes.

The namespace is defined in the xmlns attribute of the element's opening tag.

The syntax of namespace declaration is as follows. xmlns:Prefix="URI".

(3) PHP creates XML document

It is probably useless, just keep echoing. .

Note: This is an XML document, not an object.

(4) SimpleXML (SimpleXML function in PHP implements reading, writing and browsing of XML documents)

Main function:

Create xml object (3 methods can be used , specific self-check)

Traverse the child elements, use the children() function and the foreach statement.

Traverse attributes, attribute() function.

You can also access specific node elements and attributes. Assign a value (access) to a child element through its name, or assign a value (access) to a child element's attribute through its array of names.

That is, array: attribute: [], arrow: element name (label): ->.

For example: echo $xml -> book[0] -> computer['name'] ;

The modification of the data in the simplexml object is the modification in the system memory . The original document has not changed.

When you close the web page or clear the memory, the data will be restored.

How to save a modified simplexml object?

Use the asXML() method. First format the data in the simpleXML object into XML format.

Then use the file() series of functions to save the data to the XML file.

:: simpleXML cannot dynamically create XML, which requires DOM to achieve.

But DOM consumes a lot of resources.

is also very troublesome. . It's of no use. .

Note: Since the process of learning PHP only involves some XML, the content is relatively fragmented. I will post it again after learning the system. Please forgive me.

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