Regular expression to remove CSS comments

Question

I want to write the regular expression in php for matching the line within a double and single quotes. Actually I am writing the code for removing comment lines in css file.

Like:

"/* I don't want to remove this line */"

but

/* I want to remove this line */

Eg:

- valid code /* comment */ next valid code "/* not a comment */" /* this is comment */

Expected result:

- valid code next valid code "/* not a comment */"

Please any one give me a regular expression in php for my requirement.

You may simply want to use an already existing compressor instead of parsing CSS yourself, unless you have some very specific reason to do so. See CSS - How to remove comments and make CSS one line. Also: Don't Do It. — deceze
– deceze ♦, Commented Oct 21, 2010 at 5:09

Luke Stevenson · Accepted Answer · 2014-11-28 02:02:14Z

17

The following should do it:

preg_replace( '/\s*(?!<\")\/\*[^\*]+\*\/(?!\")\s*/' , '' , $theString );

Test case:

$theString = '- valid code /* comment */ next valid code "/* not a comment */" /* this is comment */';

preg_replace( '/(?!<\")\/\*[^\*]+\*\/(?!\")/' , ' ' , $theString );

# Returns 'valid code next valid code "/* not a comment */" '

Revision : 28 Nov 2014

As per comments from @hexalys, who referred to http://www.catswhocode.com/blog/3-ways-to-compress-css-files-using-php

The updated regular expression, as per that article, is:

preg_replace( '!/\*[^*]*\*+([^/][^*]*\*+)*/!' , '' , $theString );

edited Nov 28, 2014 at 2:02

answered Oct 21, 2010 at 6:34

Luke Stevenson

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6 Comments

hexalys Over a year ago

This has issues with the universal * selector at the end of css rules. e.g. .class > *{}

Luke Stevenson Over a year ago

@hexalys: Thanks for the comment - I'd love to revise my answer based on this new info. Can you email me the affected CSS code at [email protected] so I can do some testing and adjust my solution?

hexalys Over a year ago

You can test any universal selector. It may have been related to comments inside the brackets, as often do. e.g. .class > *{/*comments*/ } I ended up using the regex here.

vee Over a year ago

The updated 2014 still matched this -> li:before {content: "a/*b*/";}.

vee Over a year ago

^(\s*)\Q/*\E[\s\S]+?\Q*/\E$(\R+) This will be matched from beginning of line (^) and follow with zero or more space ((\s*)) ...until end ($) with new line ((\R+)). It is not perfect but it is just for prevent matching comment inside string.

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