Preg_match for a date

Question

Hello everyone,

I am trying to match a date in PHP using preg_match, split it and assign parts of it to an array, the date looks like "20100930", here is the code I am using:

// Make the tor_from date look nicer
$nice_from = $_POST['tor_from'];

$matches = array();
$ideal_from = '';
preg_match('/\d{4}\\d{2}\\d{2}\/', $nice_from, $matches, PREG_OFFSET_CAPTURE, 0);
// if (isset($matches[0])) $nice_from = $matches[0];
echo $matches[0];
echo "<br />";
echo $matches[1];
echo "<br />";
echo $matches[2];
echo "<br />";
echo $matches[3];
echo "<br />";

Ive been using: http://php.net/manual/en/function.preg-match.php and http://stackoverflow.com/questions/1179165/php-preg-match-question to formulate ideas on how to do this, however I have had no luck in getting it to work. Any help would be greatly appreciated.

Answer 1

You need to put some parenthesis around the patterns that you would like to show up in $matches. Also i don't think you want the double \\ in between your \d's because that will escape the second \ and leave you matching a literal 'd'.

Answer 2

Although regex isn't really a good solution for parsing a date in YYYYMMDD format, let's walk through why your pattern isn't working.

Your pattern \d{4}\\d{2}\\d{2}\ says: "match 4 digits (\d{4}), followed by a backslash character (\\), followed by the letter d twice (d{2}), followed by another backslash (\\) and then finally another two d's (d{2})."

As you might have figure out by now, you don't want the double slashes!

\d{4}\d{2}\d{2}

Will match 4 digits, followed by 2 digits, and then another 2 digits.

Furthermore, you are not specifying any capturing groups, so your subpatterns will never be filled. What you probably meant was:

(\d{4})(\d{2})(\d{2})

See this in action at http://www.ideone.com/iAy7K. Note that there really isn't any reason in your case to be specifying the PREG_OFFSET_CAPTURE flag (which returns the position of each match) or 0 for the offset.

Answer 3

Regex is not the best way to go here if the pattern is this simple. Use substr instead:

$date = '20100930';
$year = substr($date,0,4);
$month = substr($date,4,2);
$day = substr($date,6,2);

Answer 4

Forget preg_match, use strtotime():

echo date('Y/m/d', strtotime($_POST['tor_from']));

Answer 5

It's better like this, using preg_match and indexed names.

$res = preg_match("/(?P<year>[0-9]{4})(?P<month>[0-9]{2})(?P<day>[0-9]{2})/", $date, $matches);

And Matches will look like:,

array('year' => 2010, 'month' => 12, 'day' => 07);

Cheers.