Question

I am doing a academic work that I need to use parser and lexer generator for php.
I searched on the internet and I found this

The problem is create the grammar and plex file.
For example:

<?php
class blah {
/*!lex2php
%input $this->data
%counter $this->N
%token $this->token
%value $this->value
%line $this->line
variable = @/?:([a-zA-Z0-9_]+)/?@
*/
/*!lex2php
variable {$a = 1;}
*/
}
?>

Someone can explain me that code please?

Answer 1

The first comment block is used for declarations. All the % declaration are mostly for internal use, and not very relevant at this stage.
The variable = @/?:([a-zA-Z0-9_]+)/?@ is interesting though. It defines a nonterminal symbol variable, defined by the regex @/?:([a-zA-Z0-9_]+)/?@.

If you generate your lexer using this plex file and feed it something like this:

234lksdf lskdjf324 kl234jd

The tokenstream would be as follows:

token: variable
value: 234lksdf 

token: variable
value: lskdjf324 

token: variable
value: kl234jd