kukulich / nikic-php-parser

A PHP parser written in PHP

PHP Parser

This is a PHP 5.2 to PHP 8.0 parser written in PHP. Its purpose is to simplify static code analysis and manipulation.

Documentation for version 4.x (stable; for running on PHP >= 7.0; for parsing PHP 5.2 to PHP 8.0).

Documentation for version 3.x (unsupported; for running on PHP >= 5.5; for parsing PHP 5.2 to PHP 7.2).

Features

The main features provided by this library are:

• Parsing PHP 5, PHP 7, and PHP 8 code into an abstract syntax tree (AST).
  • Invalid code can be parsed into a partial AST.
  • The AST contains accurate location information.
• Dumping the AST in human-readable form.
• Converting an AST back to PHP code.
  • Experimental: Formatting can be preserved for partially changed ASTs.
• Infrastructure to traverse and modify ASTs.
• Resolution of namespaced names.
• Evaluation of constant expressions.
• Builders to simplify AST construction for code generation.
• Converting an AST into JSON and back.

Quick Start

Install the library using composer:

php composer.phar require nikic/php-parser

Parse some PHP code into an AST and dump the result in human-readable form:

<?php
use PhpParser\Error;
use PhpParser\NodeDumper;
use PhpParser\ParserFactory;

$code = <<<'CODE'
<?php

function test($foo)
{
    var_dump($foo);
}
CODE;

$parser = (new ParserFactory)->create(ParserFactory::PREFER_PHP7);
try {
    $ast = $parser->parse($code);
} catch (Error $error) {
    echo "Parse error: {$error->getMessage()}\n";
    return;
}

$dumper = new NodeDumper;
echo $dumper->dump($ast) . "\n";

This dumps an AST looking something like this:

array(
    0: Stmt_Function(
        byRef: false
        name: Identifier(
            name: test
        )
        params: array(
            0: Param(
                type: null
                byRef: false
                variadic: false
                var: Expr_Variable(
                    name: foo
                )
                default: null
            )
        )
        returnType: null
        stmts: array(
            0: Stmt_Expression(
                expr: Expr_FuncCall(
                    name: Name(
                        parts: array(
                            0: var_dump
                        )
                    )
                    args: array(
                        0: Arg(
                            value: Expr_Variable(
                                name: foo
                            )
                            byRef: false
                            unpack: false
                        )
                    )
                )
            )
        )
    )
)

Let's traverse the AST and perform some kind of modification. For example, drop all function bodies:

use PhpParser\Node;
use PhpParser\Node\Stmt\Function_;
use PhpParser\NodeTraverser;
use PhpParser\NodeVisitorAbstract;

$traverser = new NodeTraverser();
$traverser->addVisitor(new class extends NodeVisitorAbstract {
    public function enterNode(Node $node) {
        if ($node instanceof Function_) {
            // Clean out the function body
            $node->stmts = [];
        }
    }
});

$ast = $traverser->traverse($ast);
echo $dumper->dump($ast) . "\n";

This gives us an AST where the Function_::$stmts are empty:

array(
    0: Stmt_Function(
        byRef: false
        name: Identifier(
            name: test
        )
        params: array(
            0: Param(
                type: null
                byRef: false
                variadic: false
                var: Expr_Variable(
                    name: foo
                )
                default: null
            )
        )
        returnType: null
        stmts: array(
        )
    )
)

Finally, we can convert the new AST back to PHP code:

use PhpParser\PrettyPrinter;

$prettyPrinter = new PrettyPrinter\Standard;
echo $prettyPrinter->prettyPrintFile($ast);

This gives us our original code, minus the var_dump() call inside the function:

<?php

function test($foo)
{
}

For a more comprehensive introduction, see the documentation.

Documentation

1. Introduction
2. Usage of basic components

Component documentation:

• Walking the AST
  • Node visitors
  • Modifying the AST from a visitor
  • Short-circuiting traversals
  • Interleaved visitors
  • Simple node finding API
  • Parent and sibling references
• Name resolution
  • Name resolver options
  • Name resolution context
• Pretty printing
  • Converting AST back to PHP code
  • Customizing formatting
  • Formatting-preserving code transformations
• AST builders
  • Fluent builders for AST nodes
• Lexer
  • Lexer options
  • Token and file positions for nodes
  • Custom attributes
• Error handling
  • Column information for errors
  • Error recovery (parsing of syntactically incorrect code)
• Constant expression evaluation
  • Evaluating constant/property/etc initializers
  • Handling errors and unsupported expressions
• JSON representation
  • JSON encoding and decoding of ASTs
• Performance
  • Disabling Xdebug
  • Reusing objects
  • Garbage collection impact
• Frequently asked questions
  • Parent and sibling references