ANTLR4
ANTLR, ANother Tool for Language Recognition, currently at its 4th major version, is a parser generator: given a formal grammar describing a language’s syntax, it generates a lexer and a parser for that language, in a target language of choice, such as Java, C#, Python, Go or JavaScript. There is no first-class PHP target, though community-maintained backends exist.
ANTLR4 grammars are LL(*)-based and produce a parse tree, which can then be walked with a generated Listener or Visitor. It is widely used to build DSLs, configuration-file parsers, and new implementations of existing languages, including some PHP parsers used by third-party tooling.
Most PHP static analyzers do not rely on ANTLR: they use PHP’s own tokenizer, then build their own AST directly, tailored to the needs of static analysis, rather than going through a generic, grammar-driven parser.