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Welcome to the parse-yapphp wiki!

Description

This is Parse::Yapphp, a yacc-like parser compiler that generates fully reentrant LALR(1) PHP parser classes.

Please refer to the project's README.md and the POD sections in the respective source packages for in-depth (legacy) documentation.

Usage

Compiling grammar

Compilation will always create three files: the parser, the driver and a lexer interface.

yapphp -m My\\Project\\Parser\\Parser -d my/project/parser/ Parser.py

This will create Parser.php, ParserDriver.php and LexerInterface.php in the directory my/project/parser from the grammar file Parser.py. The three PHP classes will reside in the My\Project\Parser namespace.

Writing grammar

This section will not dive deeply into how to write yacc-like parser grammar; it will highlight the differences introduced by this module though and how to access rule values in PHP.

# Arbitrary rule
statements : statements ';' statement
                    # This is the semantic action in PHP
                    { return new StatementNode($_[1], $_[3]) }
           | statement
                    # Second rule's semantic action
                    { return new Statement($_[1]) }
           ;

Semantic actions are obviously written in PHP; they are included verbatim into the generated parser's rule array as anonymous functions. You MAY omit the terminating semicolon ';' for the final statement of the semantic action.

The argument to any semantic action is the array $_ that contains the semantic values of the rule starting at the index one (1). In the above example, the array $_ contains:

[
   1 => object, // Either `Statement` or `StatementNode`
   2 => ';',
   3 => object // Of type `Statement`
]

Credits

Parse::Yapphp is a port of Francois Desarmenien's CPAN package Parse::Yapp. This project borrows heavily from it; merely the parser output has been modified by the author to create PHP output.