PHP Regexp help

Question

I can't seem to get a handle on what this expression intends to extract:

preg_match("/^(?:[\s\*]*?@([^\*\/]+?)\s(.+))/",$line,$match);

$line is a line from a text file while $match is an array

Answer 1

Here's an explanation:

^               # match the beginning of the input
(?:             # start non-capture group 1 
  [\s*]*?       #   match any character from the set {'0x09'..'0x0D', '0x20', '*'} and repeat it zero or more times, reluctantly
  @             #   match the character '@'
  (             #   start capture group 1
    [^*/]+?     #     match any character from the set {'0x00'..')', '+'..'.', '0'..'ÿ'} and repeat it one or more times, reluctantly
  )             #   end capture group 1
  \s            #   match a whitespace character: [ \t\n\x0B\f\r]
  (             #   start capture group 2
    .+          #     match any character except line breaks and repeat it one or more times
  )             #   end capture group 2
)               # end capture group 1

An example string that the regex would match is this: * * *@abc asd

Edit:

I've released a beta version of the parser that was used to generate the explanation above. It can be downloaded here: http://big-o.nl/apps/pcreparser/pcre/PCREParser.html

Answer 2

This will match strings of the form

** *  ***@anything_that_is_not_an_asterisk_nor_a_slash   anything else

$match[1] contains "anything_that_is_not_an_asterisk_nor_a_slash" before the first space, $match[2] contains " anything else".

Answer 3

the @ make me think the pattern is trying to capture element of an email... as a ROT always document the regex.

Answer 4

Probably tries to capture lines of comment blocks like these (excluding first and last line):

/**
 * @param  $arg1 etc...
 * @return bool etc...
 */