使用Regex以多种格式捕获日期

Question

I'm working on an app which scrapes local websites to create a database of upcoming events, and I'm trying to use Regex to catch as many formats of dates as possible.

Consider the following sentence fragments:

• "The focus of the seminar, on Saturday 2nd February 2013 will be [...]"
• "Valentines Special @ The Radisson, Feb 14th"
• "On Friday the 15th of February, a special Hollywood themed [...]"
• "Symposium on Childhood Play on Friday, February 8th"
• "Hosting a craft workshop March 9th - 11th in the old [...]"

I want to be able to scan these and catch as many dates as possible. At the moment I'm doing this in what is probably a flawed way (I'm not great at regex), going through several regex statements one after the other, like this

/([0-9]+?)(st|nd|rd|th) (of)? (Jan|Feb|Mar|etc)/i
/([0-9]+?)(st|nd|rd|th) (of)? (January|February|March|Etcetera)/i
/(Jan|Feb|Mar|etc) ([0-9]+?)(st|nd|rd|th)/i
/(January|February|March|Etcetera) ([0-9]+?)(st|nd|rd|th)/i

I could merge these all into one giant regex statement, but it seems like there must be a cleaner way of doing this in php, maybe a third-party library or something?

EDIT: The regex above may have errors - it's only meant as an example.

Answer 1

I wrote a function which extracts dates out of text by using strtotime():

function parse_date_tokens($tokens) {
  # only try to extract a date if we have 2 or more tokens
  if(!is_array($tokens) || count($tokens) < 2) return false;
  return strtotime(implode(" ", $tokens));
}

function extract_dates($text) {
  static $patterns = Array(
    '/^[0-9]+(st|nd|rd|th|)?$/i', # day
    '/^(Jan(uary)?|Feb(ruary)?|Mar(ch)?|etc)$/i', # month
    '/^20[0-9]{2}$/', # year
    '/^of$/' #words
  );
  # defines which of the above patterns aren't actually part of a date
  static $drop_patterns = Array(
    false,
    false,
    false,
    true
  );
  $tokens = Array();
  $result = Array();
  $text = str_word_count($text, 1, '0123456789'); # get all words in text

  # iterate words and search for matching patterns
  foreach($text as $word) {
    $found = false;
    foreach($patterns as $key => $pattern) {
      if(preg_match($pattern, $word)) {
        if(!$drop_patterns[$key]) {
          $tokens[] = $word;
        }
        $found = true;
        break;
      }
    }

    if(!$found) {
      $result[] = parse_date_tokens($tokens);
      $tokens = Array();
    }
  }
  $result[] = parse_date_tokens($tokens);

  return array_filter($result);
}

# test
$texts = Array(
  "The focus of the seminar, on Saturday 2nd February 2013 will be [...]",
  "Valentines Special @ The Radisson, Feb 14th",
  "On Friday the 15th of February, a special Hollywood themed [...]",
  "Symposium on Childhood Play on Friday, February 8th",
  "Hosting a craft workshop March 9th - 11th in the old [...]"
);

$dates = extract_dates(implode(" ", $texts));
echo "Dates: 
";
foreach($dates as $date) {
  echo "  " . date('d.m.Y H:i:s', $date) . "
";
}

This outputs:

Dates: 
  02.02.2013 00:00:00
  14.02.2013 00:00:00
  15.02.2013 00:00:00
  08.02.2013 00:00:00
  09.03.2013 00:00:00

This solution may not be perfect and certainly has its flaws but it's a quite simple solution for your problem.