Upgrading from PHP-Parser 2.x to 3.0

The backwards-incompatible changes in this release may be summarized as follows:

The specific details of the node representation have changed in some cases, primarily to accommodate new PHP 7.1 features.
There have been significant changes to the error recovery implementation. This may affect you, if you used the error recovery mode or have a custom lexer implementation.
A number of deprecated methods were removed.

PHP version requirements

PHP-Parser now requires PHP 5.5 or newer to run. It is however still possible to parse PHP 5.2, 5.3 and 5.4 source code, while running on a newer version.

Changes to the node structure

The following changes are likely to require code changes if the respective nodes are used:

The List subnode vars has been renamed to items and now contains ArrayItems instead of plain variables.
The Catch subnode type has been renamed to types and is now an array of Names.
The TryCatch subnode finallyStmts has been replaced with a finally subnode that holds an explicit Finally node.
The type subnode on Class, ClassMethod and Property has been renamed to flags. The type subnode has retained for backwards compatibility and is populated to the same value as flags. However, writes to type will not update flags and use of type is discouraged.

The following changes are unlikely to require code changes:

The ClassConst constructor changed to accept an additional flags subnode.
The Trait constructor now has the same form as the Class and Interface constructors: It takes an array of subnodes. Unlike classes/interfaces, traits can only have a stmts subnode.
The Array subnode items may now contain null elements (due to destructuring).
void and iterable types are now stored as strings if the PHP 7 parser is used. Previously these would have been represented as Name instances.

Changes to error recovery mode

Previously, error recovery mode was enabled by setting the throwOnError option to false when creating the parser, while collected errors were retrieved using the getErrors() method:

$lexer = ...;
$parser = (new ParserFactory)->create(ParserFactor::ONLY_PHP7, $lexer, [
    'throwOnError' => true,
]);

$stmts = $parser->parse($code);
$errors = $parser->getErrors();
if ($errors) {
    handleErrors($errors);
}
processAst($stmts);

Both the throwOnError option and the getErrors() method have been removed in PHP-Parser 3.0. Instead an instance of ErrorHandler\Collecting should be passed to the parse() method:

$lexer = ...;
$parser = (new ParserFactory)->create(ParserFactor::ONLY_PHP7, $lexer);

$errorHandler = new ErrorHandler\Collecting;
$stmts = $parser->parse($code, $errorHandler);
if ($errorHandler->hasErrors()) {
    handleErrors($errorHandler->getErrors());
}
processAst($stmts);

Multiple parser fallback in error recovery mode

As a result of this change, if a Multiple parser is used (e.g. through the ParserFactory using PREFER_PHP7 or PREFER_PHP5), it will now return the result of the first non-throwing parse. As parsing never throws in error recovery mode, the result from the first parser will always be returned.

The PHP 7 parser is a superset of the PHP 5 parser, with the exceptions that =& new and global $$foo->bar are not supported (other differences are in representation only). The PHP 7 parser will be able to recover from the error in both cases. For this reason, this change will likely pass unnoticed if you do not specifically test for this syntax.

It is possible to restore the precise previous behavior with the following code:

$lexer = ...;
$parser7 = new Parser\Php7($lexer);
$parser5 = new Parser\Php5($lexer);

$errors7 = new ErrorHandler\Collecting();
$stmts7 = $parser7->parse($code, $errors7);
if ($errors7->hasErrors()) {
    $errors5 = new ErrorHandler\Collecting();
    $stmts5 = $parser5->parse($code, $errors5);
    if (!$errors5->hasErrors()) {
        // If PHP 7 parse has errors but PHP 5 parse has no errors, use PHP 5 result
        return [$stmts5, $errors5];
    }
}
// If PHP 7 succeeds or both fail use PHP 7 result
return [$stmts7, $errors7];

Error handling in the lexer

In order to support recovery from lexer errors, the signature of the startLexing() method changed to optionally accept an ErrorHandler:

// OLD
public function startLexing($code);
// NEW
public function startLexing($code, ErrorHandler $errorHandler = null);

If you use a custom lexer with overridden startLexing() method, it needs to be changed to accept the extra parameter. The value should be passed on to the parent method.

Error checks in node constructors

The constructors of certain nodes used to contain additional checks for semantic errors, such as creating a try block without either catch or finally. These checks have been moved from the node constructors into the parser. This allows recovery from such errors, as well as representing the resulting (invalid) AST.

This means that certain error conditions are no longer checked for manually constructed nodes.

Removed methods, arguments, options

The following methods, arguments or options have been removed:

Comment::setLine(), Comment::setText(): Create new Comment instances instead.
Name::set(), Name::setFirst(), Name::setLast(), Name::append(), Name::prepend(): Use Name::concat() in combination with Name::slice() instead.
Error::getRawLine(), Error::setRawLine(). Use Error::getStartLine() and Error::setStartLine() instead.
Parser::getErrors(). Use ErrorHandler\Collecting instead.
$separator argument of Name::toString(). Use strtr() instead, if you really need it.
$cloneNodes argument of NodeTraverser::__construct(). Explicitly clone nodes in the visitor instead.
throwOnError parser option. Use ErrorHandler\Collecting instead.

Miscellaneous

The NameResolver will now resolve unqualified function and constant names in the global namespace into fully qualified names. For example foo() in the global namespace resolves to \foo(). For names where no static resolution is possible, a namespacedName attribute is added now, containing the namespaced variant of the name.
All methods on PrettyPrinter\Standard are now protected. Previously most of them were public. The pretty printer should only be invoked using the prettyPrint(), prettyPrintFile() and prettyPrintExpr() methods.
The node dumper now prints numeric values that act as enums/flags in a string representation. If node dumper results are used in tests, updates may be needed to account for this.
The constants on NameTraverserInterface have been moved into the NameTraverser class.
The emulative lexer now directly postprocesses tokens, instead of using ~__EMU__~ sequences. This changes the protected API of the emulative lexer.
The Name::slice() method now returns null for empty slices, previously new Name([]) was used. Name::concat() now also supports concatenation with null.

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