lite-lexer
A light-weight PHP-based string lexer. By defining parser blocks, a simple syntax can be defined.
The parser will then build a tree representing the parsed string. This can then be interpreted
for other uses., (*1)
I created this for a simple query language to read custom data from a model system, but it
can easily be adapted to other syntaxes. It has relatively low overhead, and based on my
testing performed fast (enough so for my application)., (*2)
Installation
This package is available via composer and can be added to a project using the command:, (*3)
$ composer require nathanntg/lite-lexer
Usage
The recommended usage is to subclass LiteLexer\Parser to define your own syntax blocks
(see the example implementation). Then you can run your parser as follows:, (*4)
$parser = new MyParser();
// parse string
$tree = $parser->parseString($string_to_parse);
// optional: remove unneeded leaves and branches
$tree->prune();
// print debugging tree
$tree->debug();
Example Implementation
The example folder contains a QueryParser class that implements the parser needed
to read a basic query language. Specifically, given an input string like the following:, (*5)
customer.namelast='' AND customer.namefirst = '' OR ( customer.namelast='' AND customer.namefirst='' ) ORDER customer.namelast DESC , customer.namelast LIMIT 2
It will produce the following parse tree:, (*6)
root
query
conditions_main
condition_set_values
conditions
condition
condition_standard
column; raw "customer.namelast"; customer.namelast
operator
unnamed leaf; raw "="; =
value
value_string; raw "''";
condition_operator
unnamed leaf; raw "AND"; AND
conditions
condition
condition_standard
column; raw "customer.namefirst"; customer.namefirst
operator
unnamed leaf; raw "="; =
value
value_string; raw "''";
condition_operator
unnamed leaf; raw "OR"; OR
conditions
condition_set
unnamed leaf; raw "("; (
condition_set_values
conditions
condition
condition_standard
column; raw "customer.namelast"; customer.namelast
operator
unnamed leaf; raw "="; =
value
value_string; raw "''";
condition_operator
unnamed leaf; raw "AND"; AND
conditions
condition
condition_standard
column; raw "customer.namefirst"; customer.namefirst
operator
unnamed leaf; raw "="; =
value
value_string; raw "''";
unnamed leaf; raw ")"; )
order_by_main
unnamed leaf; raw "ORDER"; ORDER
order_by_columns
order_by_column
column; raw "customer.namelast"; customer.namelast
order_by_direction
unnamed leaf; raw "DESC"; DESC
order_by_column
column; raw "customer.namelast"; customer.namelast
limit_main
unnamed leaf; raw "LIMIT"; LIMIT
limit_count; raw "2"; 2
Testing
You can run the PHPUnit tests using the following command (assuming installed via
composer, and includes the developer requirements):, (*7)
$ vendor/bin/phpunit tests
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