Demo for format preserving AST transformation

demo.php

<?php

/* This demo replaces all unqualified function calls and namespaced lookups
 * with fully qualified ones. Apart from this change all formatting should
 * be preserved. */

use PhpParser\Lexer;
use PhpParser\Parser;
use PhpParser\NodeTraverser;
use PhpParser\NodeVisitor;
use PhpParser\NodeVisitorAbstract;
use PhpParser\PrettyPrinter;
use PhpParser\Error;
use PhpParser\Node;

$dir = /* directory to operate on */;

require __DIR__ . '/vendor/autoload.php';

class NameFullyQualifier extends NodeVisitorAbstract {
    public function leaveNode(Node $node) {
        if ($node instanceof Node\Name
            && $node->hasAttribute('namespacedName')
            && !in_array(strtolower($node), ['true', 'false', 'null'])
        ) {
            return new Node\Name\FullyQualified($node);
        }
        return null;
    }
}

$lexer = new Lexer\Emulative([
    'usedAttributes' => [
        'comments',
        'startLine', 'endLine',
        'startTokenPos', 'endTokenPos',
    ],
]);
$parser = new Parser\Php7($lexer, [
    'useIdentifierNodes' => true,
    'useConsistentVariableNodes' => true,
    'useExpressionStatements' => true,
    'useNopStatements' => false,
]);
$nameResolver = new NodeVisitor\NameResolver(null, [
    'replaceNodes' => false
]);

$traverser = new NodeTraverser();
$traverser->addVisitor(new NodeVisitor\CloningVisitor());
$traverser->addVisitor($nameResolver);
$traverser->addVisitor(new NameFullyQualifier());

$printer = new PrettyPrinter\Standard();

$it = new RecursiveIteratorIterator(
    new RecursiveDirectoryIterator($dir),
    RecursiveIteratorIterator::LEAVES_ONLY
);
foreach ($it as $file) {
    if (!preg_match('/\.php$/', $file)) {
        continue;
    }

    try {
        $code = file_get_contents($file);
        $origStmts = $parser->parse($code);
        $newCode = $printer->printFormatPreserving(
            $traverser->traverse($origStmts),
            $origStmts,
            $lexer->getTokens()
        );
        file_put_contents($file, $newCode);
    } catch (Error $e) {
        echo "Parser error in $file: {$e->getMessage()}\n";
    }
}