PHP Parser

This is a PHP parser written in PHP. It's purpose is to simplify static code analysis and manipulation.

Note: This project is highly experimental. It may not always function correctly.

Components

This package currently bundles several components:

• The Parser itself
• A NodeDumper to dump the nodes to a human readable string representation
• A NodeTraverser to traverse and modify the node tree
• A PrettyPrinter to translate the node tree back to PHP

Autoloader

In order to automatically include required files PHPParser_Autoloader can be used:

require_once 'path/to/phpparser/lib/PHPParser/Autoloader.php';
PHPParser_Autoloader::register();

Parser and ParserDebug

Parsing is performed using PHPParser_Parser->parse(). This method accepts a PHPParser_Lexer as the only parameter and returns an array of statement nodes. If an error occurs it throws a PHPParser_Error.

$code = '<?php // some code';

try {
    $parser = new PHPParser_Parser;
    $stmts = $parser->parse(new PHPParser_Lexer($code));
} catch (PHPParser_Error $e) {
    echo 'Parse Error: ', $e->getMessage();
}

The PHPParser_ParserDebug class also parses a PHP code, but outputs a debug trace while doing so.

Node Tree

The output of the parser is an array of statement nodes. All nodes are instances of PHPParser_NodeAbstract. Furthermore nodes are divided into three categories:

• PHPParser_Node_Stmt: A statement
• PHPParser_Node_Expr: An expression
• PHPParser_Node_Scalar: A scalar (which is a string, a number, aso.) PHPParser_Node_Scalar inherits from PHPParser_Node_Expr.

Each node may have subnodes. For example PHPParser_Node_Expr_Plus has two subnodes, namely left and right, which represend the left hand side and right hand side expressions of the plus operation. Subnodes are accessed as normal properties:

$node->left

The subnodes which a certain node can have are documented as @property doccomments in the respective files.

Additionally all nodes have two methods, getLine() and getDocComment(). getLine() returns the line a node started in. getDocComment() returns the doccomment before the node or null if there was none.

NodeDumper

Nodes can be dumped into a string representation using the PHPParser_NodeDumper->dump() method:

$code = <<<'CODE'
<?php
    function printLine($msg) {
        echo $msg, "\n";
    }

    printLine('Hallo World!!!');
CODE;

try {
    $parser = new PHPParser_Parser;
    $stmts = $parser->parse(new PHPParser_Lexer($code));

    $nodeDumper = new PHPParser_NodeDumper;
    echo '<pre>' . htmlspecialchars($nodeDumper->dump($stmts)) . '</pre>';
} catch (PHPParser_Error $e) {
    echo 'Parse Error: ', $e->getMessage();
}

This script will have an output similar to the following:

array(
    0: Stmt_Func(
        byRef: false
        name: printLine
        params: array(
            0: Stmt_FuncParam(
                type: null
                name: msg
                byRef: false
                default: null
            )
        )
        stmts: array(
            0: Stmt_Echo(
                exprs: array(
                    0: Variable(
                        name: msg
                    )
                    1: Scalar_String(
                        value:

                    )
                )
            )
        )
    )
    1: Expr_FuncCall(
        func: Name(
            parts: array(
                0: printLine
            )
        )
        args: array(
            0: Expr_FuncCallArg(
                value: Scalar_String(
                    value: Hallo World!!!
                )
                byRef: false
            )
        )
    )
)

NodeTraverser

The node traverser allows traversing the node tree using a visitor class. A visitor class must implement the NodeVisitorInterface, which defines the following four methods:

public function beforeTraverse(&$node);
public function enterNode(PHPParser_NodeAbstract &$node);
public function leaveNode(PHPParser_NodeAbstract &$node);
public function afterTraverse(&$node);

The beforeTraverse method is called once before the traversal begins and is passed the node the traverser was called with. This method can be used for resetting values before traversation or preparing the tree for traversal.

The afterTraverse method is similar to the beforeTraverse method, with the only difference that it is called once after the traversal.

The enterNode and leaveNode methods are called on every node, the former when it is entered, i.e. before its subnodes are traversed, the latter when it is left.

The node is passed into all four functions by reference, i.e. the node may be transformed or even replaced in any way. (As the node is passed by reference it obviously shouldn't be returned after modifiation.) Additionally leaveNode can return two special values: If false is returned the current node will be completely deleted. If an array is returned the current node will be replaced with with an array of other nodes. I.e. if in array(A, B, C) the node B should be replaced with array(X, Y, Z) the result will be array(A, X, Y, Z, C).

The above described visitors are registered in the NodeTraverser class:

$visitor = new MyVisitor;

$traverser = new PHPParser_NodeTraverser;
$traverser->addVisitor($visitor);

$stmts = $parser->parse($lexer);

// ->traverse() directly modifies $stmts. Do *not* write $stmts = $traverser->traverse($stmts);
$traverser->traverse($stmts);

With MyVisitor being something like that:

class MyVisitor extends PHPParser_NodeVisitorAbstract
{
    public function enterNode(PHPParser_NodeAbstract &$node) {
        // ...
    }
}

As you can see above you don't need to define all four methods if you extend PHPParser_NodeVisitorAbstract instead of directly implementing the interface.

PrettyPrinter

The pretty printer compiles nodes back to PHP code. "Pretty printing" here is just the formal name of the process and does not mean that the output is in any way pretty.

$prettyPrinter = new PHPParser_PrettyPrinter_Zend;
echo '<pre>' . htmlspecialchars($prettyPrinter->prettyPrint($stmts)) . '</pre>';

For the code mentioned in the above section this should create the output:

function printLine($msg)
{
    echo $msg, "\n";
}
printLine('Hallo World!!!');

You can also pretty print only a single expression using the prettyPrintExpr() method.