PEG-php parsing if statement

Question

Good day. Just started to use PEG. I'm familiar with wp:peg and some other theory, but still can't understand how it internally works.

My task is to parse expressions like

if($a=='qwerty' && $b>2 || $c<=5)
     print 'something';
endif;

Body of is statement contains only print operator and nothing else, but it has complex condition.

My thinking about it:

/*!* Calculator

Int: /[0-9]+/
Var: /\$[a-z]+/
tThen: /then{1}/
tIf: /if{1}/
tElse: /else{1}/
tEndif: /endif{1}/

block: /.+/

condEq: Var '==' ( Int | Var ) * 

condStatement: '(' condEq ')'
  function condEq( &$result, $sub ) {
    if( eval($sub['text'].';') ) {
        $result['text'] = 'true';
    }
    else {
        $result['text'] = 'false';
    }
  }

 ifStatement: tIf condStatement

 Expr: ifStatement

 */

But I believe this task has better solution:) Can you help me with it? Thanks.