A PHP parser written in PHP
PHP Yacc
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README.md

PHP Parser

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This is a PHP 5.2 to PHP 7.2 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 7.2).

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 and PHP 7 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