AST_builders.markdown

AST builders

When PHP-Parser is used to generate (or modify) code by first creating an Abstract Syntax Tree and then using the pretty printer to convert it to PHP code, it can often be tedious to manually construct AST nodes. The project provides a number of utilities to simplify the construction of common AST nodes.

Fluent builders

The library comes with a number of builders, which allow creating node trees using a fluent interface. Builders are created using the BuilderFactory and the final constructed node is accessed through getNode(). Fluent builders are available for the following syntactic elements:

• namespaces and use statements
• classes, interfaces and traits
• methods, functions and parameters
• properties

Here is an example:

use PhpParser\BuilderFactory;
use PhpParser\PrettyPrinter;
use PhpParser\Node;

$factory = new BuilderFactory;
$node = $factory->namespace('Name\Space')
    ->addStmt($factory->use('Some\Other\Thingy')->as('SomeClass'))
    ->addStmt($factory->useFunction('strlen'))
    ->addStmt($factory->useConst('PHP_VERSION'))
    ->addStmt($factory->class('SomeOtherClass')
        ->extend('SomeClass')
        ->implement('A\Few', '\Interfaces')
        ->makeAbstract() // ->makeFinal()

        ->addStmt($factory->useTrait('FirstTrait'))

        ->addStmt($factory->useTrait('SecondTrait', 'ThirdTrait')
            ->and('AnotherTrait')
            ->with($factory->traitUseAdaptation('foo')->as('bar'))
            ->with($factory->traitUseAdaptation('AnotherTrait', 'baz')->as('test'))
            ->with($factory->traitUseAdaptation('AnotherTrait', 'func')->insteadof('SecondTrait')))

        ->addStmt($factory->method('someMethod')
            ->makePublic()
            ->makeAbstract() // ->makeFinal()
            ->setReturnType('bool') // ->makeReturnByRef()
            ->addParam($factory->param('someParam')->setType('SomeClass'))
            ->setDocComment('/**
                              * This method does something.
                              *
                              * @param SomeClass And takes a parameter
                              */')
        )

        ->addStmt($factory->method('anotherMethod')
            ->makeProtected() // ->makePublic() [default], ->makePrivate()
            ->addParam($factory->param('someParam')->setDefault('test'))
            // it is possible to add manually created nodes
            ->addStmt(new Node\Expr\Print_(new Node\Expr\Variable('someParam')))
        )

        // properties will be correctly reordered above the methods
        ->addStmt($factory->property('someProperty')->makeProtected())
        ->addStmt($factory->property('anotherProperty')->makePrivate()->setDefault(array(1, 2, 3)))
    )

    ->getNode()
;

$stmts = array($node);
$prettyPrinter = new PrettyPrinter\Standard();
echo $prettyPrinter->prettyPrintFile($stmts);

This will produce the following output with the standard pretty printer:

<?php

namespace Name\Space;

use Some\Other\Thingy as SomeClass;
use function strlen;
use const PHP_VERSION;
abstract class SomeOtherClass extends SomeClass implements A\Few, \Interfaces
{
    use FirstTrait;
    use SecondTrait, ThirdTrait, AnotherTrait {
        foo as bar;
        AnotherTrait::baz as test;
        AnotherTrait::func insteadof SecondTrait;
    }
    protected $someProperty;
    private $anotherProperty = array(1, 2, 3);
    /**
     * This method does something.
     *
     * @param SomeClass And takes a parameter
     */
    public abstract function someMethod(SomeClass $someParam) : bool;
    protected function anotherMethod($someParam = 'test')
    {
        print $someParam;
    }
}

Additional helper methods

The BuilderFactory also provides a number of additional helper methods, which directly return nodes. The following methods are currently available:

• val($value): Creates an AST node for a literal value like 42 or [1, 2, 3].
• var($name): Creates variable node.
• args(array $args): Creates an array of function/method arguments, including the required Arg wrappers. Also converts literals to AST nodes.
• funcCall($name, array $args = []): Create a function call node. Converts $name to a Name node and normalizes arguments.
• methodCall(Expr $var, $name, array $args = []): Create a method call node. Converts $name to an Identifier node and normalizes arguments.
• staticCall($class, $name, array $args = []): Create a static method call node. Converts $class to a Name node, $name to an Identifier node and normalizes arguments.
• new($class, array $args = []): Create a "new" (object creation) node. Converts $class to a Name node.
• constFetch($name): Create a constant fetch node. Converts $name to a Name node.
• classConstFetch($class, $name): Create a class constant fetch node. Converts $class to a Name node and $name to an Identifier node.
• propertyFetch($var, $name): Creates a property fetch node. Converts $name to an Identifier node.
• concat(...$exprs): Create a tree of BinaryOp\Concat nodes for the given expressions.

These methods may be expanded on an as-needed basis. Please open an issue or PR if a common operation is missing.