How to use php parser

"php parser" is used to generate template code, or use the generated abstract syntax tree for static analysis; "php parser" is a PHP abstract syntax tree parsing tool developed by nikic, while taking into account the ease of interface It has many advantages such as application, structural introduction, and complete tool chain.

The operating environment of this article: Windows 10 system, PHP version 8.1, Dell G3 computer

How to use php parser

PHP Parser is a PHP abstract syntax tree (AST) parsing tool developed by nikic. PHP Parser also takes into account many advantages such as easy-to-use interface, simple structure, and complete tool chain. In engineering, PHP Paser is commonly used to generate template code, or the abstract syntax tree generated by it is used for static analysis.

PHP Parser is a project for source code parsing. It is worth mentioning that it is written in pure PHP. For PHP programmers, they can use their familiar language to do source code processing such as static analysis. Undoubtedly a great convenience.

PHP is a dynamic language and its performance is not high, so using PHP Parser to analyze PHP code has poor performance. Fortunately, code analysis scenarios generally do not have high performance requirements.

The token_get_all function that comes with PHP uses the syntax analyzer of the Zend engine to split the source code into a series of tokens. Although these tokens can be used to complete many code analysis and processing tasks, because the token structure is too primitive, traversal It is very inconvenient to operate. Also based on the results of token_get_all analysis, the famous code standardization tool PHP CodeSniffer makes code analysis easier by doing a lot of processing on tokens and providing a series of search and traversal interfaces.

PHP Parser can generate an abstract syntax tree (AST, or Abstract Syntax Tree) structure corresponding to PHP code, greatly simplifying source code traversal and other operations.

Example of parsing results of PHP parser

For the following piece of PHP code:

<?php
echo &#39;Hi&#39;, &#39;World&#39;;

The tree structure generated after parsing is as follows:

array(
    0: Stmt_Echo(
        exprs: array(
            0: Scalar_String(
                value: Hi
            )
            1: Scalar_String(
                value: World
            )
        )
    )
)

The structure of the syntax tree generated by PHP parser

In order to further simplify the operation, PHP Parser groups language nodes (Node):

PhpParserNodeStmt is a statement (statement) Nodes, including language structures that have no return value and do not appear in expressions, such as class definitions;

PhpParserNodeExpr is an expression (expression) node, including language structures that have return values ​​and can appear in expressions. , such as $var (PhpParserNodeExprVariable) and func() (PhpParserNodeExprFuncCall), etc.;

PhpParserNodeScalar scalar (Scalar) node, such as: 'string' (PhpParserNodeScalarString_), 0 (PhpParserNodeScalarLNumber) and magic constants such as __FILE__ (PhpParserNodeScalarMagicConstF ile ) wait. They are also expressions, all inherited from expression nodes;

Other nodes, such as: name node (PhpParserNodeName) and parameter node (PhpParserNodeArg)

Any node class name and PHP keyword If there is a conflict, the class name of the node will all end with _, such as PhpParserNodeScalarString_.

What can PHP Parser do?

In addition to simply parsing the source code into an abstract syntax tree, it also comes with the following features:

Code generation, which can convert the abstract syntax tree into PHP code

Conversion between abstract syntax tree and XML

Export the syntax tree structure for easy viewing

The base class for traversing and modifying the syntax tree structure (node ​​traverser and node visitor)

Support namespace node visitors

Using syntax tree traversal, we can write programs to analyze code problems. Combined with features such as code generation and syntax tree structure traversal modification, we can automate code refactoring and more.

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