php里面的mark,PHP CommonMarkCQL 用法手册

CommonMark查询语言(CQL)是一种用于描述如何遍历CommonMark节点树的领域特定语言(DSL)。CQL通过一系列指令定义路径，如firstChild、lastChild等来遍历树结构。此外，还支持循环遍历子节点或兄弟节点，并可通过类型约束限制遍历范围。

简介

CommonMark Query Language is a DSL for describing how to travel through a CommonMark Node tree implemented as a parser and compiler for a small set of instructions, and a virtual machine for executing those instructions.

Paths:

In it's most simplistic form, a CQL query combines the following paths and / to describe how to travel through a tree:

firstChild

lastChild

parent

For example, /firstChild/lastChild would travel to the last child node of the first child node.

Loops

CQL can be instructed to loop, for example through the children of, or siblings to a particular node, by using the path children, or siblings. For example, /firstChild/children will travel to all the children of the first child node.

Subqueries

CQL can be instructed how to travel by using a subquery like [/firstChild]. For example, /firstChild/children[/firstChild] will travel to the first child node of all the children of the first child node.

Loop Constraints

While looping, CQL can be instructed to constrict the travelled path to nodes of particular type. For example /children(BlockQuote) will travel to the children of a node where the type is BlockQuote. The following types are recognized (case insensitively):

BlockQuote

List

Item

CodeBlock

HtmlBlock

CustomBlock

Paragraph

Heading

ThematicBreak

Text

SoftBreak

LineBreak

Code

HtmlInline

CustomInline

Emphasis

Strong

Link

Image

Types may be used as a union, for example /children(BlockQuote List) will travel to the children of a node where the type is BlockQuote or List. Types, or unions of types, may be also negated. For example /children(~BlockQuote) will travel to the children of a node where the type is not BlockQuote, and /children(~BlockQuote Paragraph) will travel to the children of a node where the type is not BlockQuote or Paragraph

Path Constraints

CQL can be instructed to create a loop to travel to a node of a particular type, at a particular path. For example, /firstChild(BlockQuote) will travel to the first child node where the type is BlockQuote. Note that like other loops for children and siblings, this kind of path can only be followed by a subquery.

Implementation Notes

While CQL has been implemented as part of the PHP CommonMark extension, it stands separately from PHP and does not use PHP's virtual machine or internal representation of values.