Stripping multiline comments using RegEx

[REMIYA]

I want to strip the single line and multi line comments wrapped in /* */.

The following RegEx does exatly that, but strips the comments also and in the strings.







//Strips all the multi-line and single-line /* */comments even in strings ""

$pattern ="/\/\\*[\\s\\S]*?\\*\//";

$replacement = "THE COMMENT HAS BEEN HERE";

echo nl2br(preg_replace($pattern, $replacement, $phpcode));







So an initial code of:





/*

This is a multiline comment

*/



/* This is a single line comment */



echo "Hi, /* This is a single line comment in a string*/";





Processed through the above RegEx returns:

THE COMMENT HAS BEEN HERE



THE COMMENT HAS BEEN HERE



echo "Hi, THE COMMENT HAS BEEN HERE";





I've done a lot of testing with RegExs, but all was in vain. So was the search through Internet.

Is there any solution to the problem using RegEx?

Please, test before you post.

[Bruce]

This kind of problem is very hard to do with regular expressions. What you need is "context", and regular expressions have no context. I can personally think of no easy way to do it with regexp searching.

What is typically done is to build a parser that keeps track of if its in a string or a comment, and does the appropriate replacement. You can use regular expressions to do the searching (for example, search for /.*?("|/\*)/ and then check $1 if it's a quote or a comment), but its an iterative process that can't be done from within a regexp itself.

[REMIYA]

What is typically done is to build a parser that keeps track of if its in a string or a comment, and does the appropriate replacement. You can use regular expressions to do the searching (for example, search for /.*?("|/\*)/ and then check $1 if it's a quote or a comment), but its an iterative process that can't be done from within a regexp itself.

Writing a whole parser is quite a work for such a task! :umm:

[sheila]

Generally, there are already parser libraries available, depending on the language you are using, and you would just grab one of those?

[REMIYA]

Thank you mates,

I have reached to the following solution:
http://php.paco.net/manual/en/function.php-strip-whitespace.php (http://php.paco.net/manual/en/function.php-strip-whitespace.php)

This is the same as php -w from the command line.

Perhaps, I'll have to save the code to a temporary file, execute the function.

And then grab the result code from the file.

I thought, wouldn't it be possible to make it dinamicaly, without saving code to temporary file.

[kitchin]

Maybe all your comments occur at the beginning of a line, and all the quoted ones do not!

[REMIYA]

The solution is PHP tokenizer, coming built with PHP5.

Why write a parser when there is already one written :)

[PaulKroll]

Well, Terra has said PHP5 is still cooking, but given the time so far, it could be closer to "the lithosphere has cooled enough to form a thin, glowing crust" stage... it might be a little while before the surface can sustain life.
- Sorry, Terra, for the "terran" motif. :)