Using preg_match to validate a string format

Question

I have an html form with an input for a sales order number which should have the format of K1234/5678. It should always start with the letter K then 4 numbers, a / and followed by another set of 4 numbers.

I'm trying to validate the formatting using preg_match and I'm getting lost in the syntax of preg_match. From http://php.net/manual/en/function.preg-match.php I've gotten close. With the following code I'm able to verify that it contains at least 1 letter, some numbers and at least 1 non- alphanumeric value.

$so= $_POST['so'];
if (preg_match(""/^(?=.*[a-z]{1})(?=.*[0-9]{4})(?=.*[^a-z0-9]{1})/i", $so))
{
    print $so;
}

What is the correct syntax to use for this? Is preg_match even the best way to do this?

Kryten · Accepted Answer · 2014-05-22 16:38:38Z

1

Try this:

preg_match("#^K[0-9]{4}/[0-9]{4}$#i", $so)

Explanation:

The # characters are regular expression delimiters - they indicate the start/end of the pattern. The ^ and $ indicate the start and end of the string - this means that it will only match if your sales order number is the only thing in the string. The letter K means match that letter, [0-9]{4} means match a digit exactly 4 times. The i at the end means a case-insensitive match - the K will match either "K" or "k".

When developing regular expressions, I often use regular expression testers - these allow you to enter your data and try a bunch of different things to refine your regex. Google PHP regex tester to find a list of tools. Also, there's a very complete reference to regular expressions at http://www.regular-expressions.info/.

answered May 22, 2014 at 16:38

Kryten

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1 Comment

meverhart913 Over a year ago

Thanks, this worked great. I will look into a regex tester, seems like they could be pretty helpful.

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