This document describes the known limitations of the current phc implementation. These limitations are things that we are aware of but that are not high on our priority list of things to deal with at the moment. However, if any of them are bothering you, let us know and we might look into it.

Comments

Representing PHP explains how we deal with comments. Most comments in a PHP script should get attached to the right token in the tree, and no comments should ever be lost. If that is not true, please send us a sample program that demonstrates where it breaks. There are a few problems that we are aware of, and there are probably others too.

Dealing with comments in a completely satisfactory way is a difficult task! The first problem with our method of dealing with comments is how we deal with whitespace in multi-line comments. Consider the following example.

<?php
   /*
    * Some comment with
    * multiple lines
    */
   foo();
?>

The problem is that the whitespace at the start of each line is included in the comment. This means that when the unparser outputs the comment, it outputs something like

<?php
   /*
    * Some comment with
       * multiple lines
       */
   foo();
?>

It is unclear how to solve this problem nicely. Suggestions are welcome :-)

Second, it is not currently possible to associate a comment with the else-clause of an if-statement. Thus, in

<?php
   // Comment 1
   if($c)
   {
      foo();
   }
   // Comment 2
   else
   {
      bar();
   }
?>

Comment 2 will be associated with the call to bar (but Comment 1 will be associated with the if-statement itself). A similar problem occurs with comments for elseif statements.

Finally, if a scope ends on a comment, that comment will be associated with the wrong node. For example, in

<?php
   if($c)
   {
      echo "Hi";
   }
   else
   {
      // Do nothing
   }

   echo "World";
?>

the comment will be associated with the echo "World" statement. A similar problem occurs when a script ends on a comment; that comment will not be lost, but will be associated with the last node in the script.

Numbers

PHP accepts invalid octal numbers such as 01090; the “incorrect tail” is silently ignored (so, this number should evaluate to 8 decimal). The phc lexical analyser will generate an “invalid token” instead which will result in a syntax error.