Sunday, July 13, 2008

Regular Expressions for username, date, ip address, color, postal code, and phone

Pasting here just to reuse them in the near future.

Here are eight examples of practical PHP regular expressions and techniques that I've used over the past few years using Perl Compatible Regular Expressions. This guide goes over the eight different validation techniques and describes briefly how they work. Usernames, telephone numbers, email addresses, and more. Here are eight examples of practical PHP regular expressions and techniques that I've used over the past few years using Perl Compatible Regular Expressions. This guide goes over the eight different validation techniques and describes briefly how they work. Usernames, telephone numbers, email addresses, and more.

Validating Usernames

Something often overlooked, but simple to do with a regular expression would be username validation. For example, we may want our usernames to be between 4 and 28 characters in length, alpha-numeric, and allow underscores.
$string = "userNaME4234432_";
if (preg_match('/^[a-z\d_]{4,28}$/i', $string)) {
echo "example 1 successful.";
}

Validating Telephone Numbers

A much more interesting example would be matching telephone numbers (US/Canada.) We'll be expecting the number to be in the following form: (###)###-####
$string = "(032)555-5555";
if (preg_match('/^(\(?[2-9]{1}[0-9]{2}\)?|[0-9]{3,3}[-. ]?)[ ][0-9]{3,3}[-. ]?[0-9]{4,4}$/', $string)) {
echo "example 2 successful.";
}

Thanks to Chris for pointing out that there are no US area codes below 200.

Again, whether the phone number is typed like (###) ###-####, or ###-###-#### it will validate successfully. There is also a little more leeway than specifically checking for enough numbers, because the groups of numbers can have or not have parenthesis, and be separated by a dash, period, or space.

Email Addresses

Another practical example would be an email address. This is fairly straightforward to do. There are three basic portions of an email address, the username, the @ symbol, and the domain name. The following example will check that the email address is in the valid form. We'll assume a more complicated form of email address, to make sure that it works well with even longer email addresses.
$string = "first.last@domain.co.uk";
if (preg_match(
'/^[^0-9][a-zA-Z0-9_]+([.][a-zA-Z0-9_]+)*[@][a-zA-Z0-9_]+([.][a-zA-Z0-9_]+)*[.][a-zA-Z]{2,4}$/',
$string)) {
echo "example 3 successful.";
}

Postal Codes

Validating Postal codes (Zip codes?,) is another practical example, but is a good example to show how ? works in regular expressions.

$string = "55324-4324";
if (preg_match('/^[0-9]{5,5}([- ]?[0-9]{4,4})?$/', $string)) {
echo "example 4 successful.";
}

What the ? does in this example is saying that the extra 4 digits at the end can either not exist, or exist- but only once. That way, whether or not they type them in, it will still validate correctly.

IP Addresses

Without pinging or making sure it's actually real, we can make sure that it's in the right form. We'll be expecting a normally formed IP address, such as 255.255.255.0.
$string = "255.255.255.0";
if (preg_match(
'^(?:25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)(?:[.](?:25[0-5]|2[0-4]\d|1\d\d|[1-9]\d|\d)){3}$',
$string)) {
echo "example 5 successful.";
}

Hexadecimal Colors

Moving right along with numbers, we could check for Hexadecimal color codes, in short hand or long hand format (#333, 333, #333333 or 333333) with an optional # symbol. This could be useful in a lot of different ways... maybe previewing CSS files? Grabbing colors off pages? The options are endless.
$string = "#666666";
if (preg_match('/^#(?:(?:[a-f\d]{3}){1,2})$/i', $string)) {
echo "example 6 successful.";
}

Multi-line Comments

- A simple way to find or remove PHP/CSS/Other languages multi-line comments could be useful as well.
$string = "/* commmmment */";
if (preg_match('/^[(/*)+.+(*/)]$/', $string)) {
echo "example 7 successful.";
}

Dates

- And my last simple, yet practical example would be dates, in my favorite MM/DD/YYYY format.
$string = "10/15/2007";
if (preg_match('/^\d{1,2}\/\d{1,2}\/\d{4}$/', $string)) {
echo "example 8 successful.";
}



The source is here.

5 comments:

Euribates said...

I'm not sure, but I think that the "underscore" character (_) is forbidden in Internet domains, so it must be excluded of the domain part of the email addresses.

A great work, your site. thank you.

bayarsaikhan said...

Yes your are right ;)

Anonymous said...

Hi,

Thank you for your examples that helps.

However, for email, according to wikipedia http://en.wikipedia.org/wiki/E-mail_address#RFC_Specification and RFC 2822, it seems much more complex to validate an email address.

Anonymous said...

Zarim ni hudalaa baina sh dee.

Anonymous said...

Sweets snippets, but the pattern for ip addresses is wrong. It also match addresses like "955.255.26.255".