<?php

use PhpParser\Node;

use PhpParser\NodeTraverser;

use PhpParser\NodeVisitorAbstract;

use PhpParser\ParserFactory;

use PhpParser\PrettyPrinter\Standard;

require 'vendor/autoload.php';

class MyNodeVisitor extends NodeVisitorAbstract

{

public function leaveNode(Node $node) {

if ($node instanceof Node\Scalar\String_) {

$node->value = 'World';

}

}

}

$code = <<<'CODE'

<?php

echo 'Hello';

CODE;

$parser = (new ParserFactory)->create(ParserFactory::PREFER_PHP7);

$traverser = new NodeTraverser;

// add your visitor

$traverser->addVisitor(new MyNodeVisitor);

$ast = $parser->parse($code);

$traverser->traverse($ast);

$prettyPrinter = new Standard();

echo $prettyPrinter->prettyPrintFile($ast);