在正则表达式中查找并替换注释块中的字符串（的一部分）

Question

I'm trying to find a certain string that can occur inside a comment block. That string can be a word, but it can also be part of a word. For instance, suppose I'm looking for the word "codex", then this word should be replace with "bindex" but even when it's part of a word, like "codexing". This should be changed to "bindexing".

The trick is, that this should only happen when this word is inside a comment block.

/* Lorem ipsum dolor sit amet, codex consectetur adipiscing elit. */

This word --> codex should not be replaced

/* Lorem ipsum dolor sit 
 * amet, codex consectetur 
 * adipiscing elit. 
 */

/** Lorem ipsum dolor sit 
 * amet, codex consectetur 
 * adipiscing elit. 
 */

// Lorem ipsum dolor sit amet, codex consectetur adipiscing elit.

# Lorem ipsum dolor sit amet, codex consectetur adipiscing elit.

------------------- Below "codex" is part of a word -------------------

/* Lorem ipsum dolor sit amet, somecodex consectetur adipiscing elit. */

/* Lorem ipsum dolor sit 
 * amet, codexing consectetur 
 * adipiscing elit. 
 */

And here also, this word --> codex should not be replaced

/** Lorem ipsum dolor sit 
 * amet, testcodexing consectetur 
 * adipiscing elit. 
 */

// Lorem ipsum dolor sit amet, __codex consectetur adipiscing elit.

# Lorem ipsum dolor sit amet, codex__ consectetur adipiscing elit.

What I have so far is this code:

$text = preg_replace ( '~(\/\/|#|\/\*).*?(codex).*?~', '$1 bindex', $text);

As you can see in this example , this isn't really working the way I'd like. It doesn't replace the word when it's inside a multiline /* */ comment block, And sometimes it removes all the text that was in front of the word "codex" as well.

How can I improve my regex so that it meets my requirements?

Answer 1

Since you're dealing with multi-line text here you should be using s modifier (DOTALL) to match text across multiple line. Also forward slash doesn't need to be escaped.

Try this code:

$text = preg_replace ( '~(//|#|/\*).*?(codex).*?~s', '$1 bindex', $text );

Answer 2

$text = preg_replace ( '~(//|#|/\*)(.*?)(codex).*?~s', '$1$2bindex', $text );

这不会删除'codex'之前的评论，例如来自anubhava的答复

Answer 3

This version can deal with any type of comments and will not fail with this kind of strings /**/ codex /**/ or /*xxxx codex codex xxxx*/ :

$pattern = <<<'LOD'
~
# definitions
(?(DEFINE)
    (?<cl> (?> [^c\n]++ | c(?!odex) )++            )
    (?<c>  (?> [^*c]++ | \*++(?!/) | c(?!odex) )++ )
)

# pattern
(?|
    (?> (?>//|\#) \g<cl>*+ | \G(?<!^) \g<cl>?+ ) \K codex (\g<cl>*+)
  |
    (?> /\* \n*+ | \G(?<!^) (?!\n) ) \g<c>*+ \K codex (\n*+) 
)  
~x
LOD;
$replacement ="bindex$3";
$result = preg_replace($pattern, $replacement, $subject);

Answer 4

Something like this using sub groups should work;

$str = preg_replace(
    '~(<!--[a-zA-Z0-9 \n]*)(MYWORD)([a-zA-Z0-9 \n]*-->)~s',
    '$1$3',
     $input
);

You will just need to create a separate rule for each type of comment, and limit the possible characters allowed inside the comment with a character class (You might prefer to use a negated character class).

Answer 5

As was written hundreds, thousands or maybe even millions of times before in different comments, Regular Expressions are NOT for parsing code, or searching for errors in one.

Consider these examples:

// code to be replaced
var a = "/*code to be replaced*/";

/* code to be replaced
var b = "*/code to be replaced"; */

There is no way for you to parse the code (and yes, finding out if a string is inside a comment block is called parsing) with REGEX.

Find a parser library, or create a diminished one of your own. If you do create one, remember all the different use-cases of the script, and in particular, how strings will affect your code.