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