10 Practical PHP Regular Expression Recipes

PHP regular expressions are used to validate character patters. For example, a zip code has the form xxxxx or optionally xxxxx-yyyy

Thanks to Gilang Chandrasa for posting the following here.

March 18th, 2009

Latest update Email validation seems quite tricky. Do you have a better solution? Let’s have email validation challenge. And give the user the best way to validate an email format.

Mastering regex or regular expression is one advantages for you as programmer, but not everyone has time to learn something.

Not knowing how regex works doesn’t mean you couldn’t use the power of regex in your project.

Bookmark this list, so you can always going back here whenever you need this regex recipes.

Update :
Never though, my post will reach so many people, and cause so many reaction. But thank you to everyone, as I myself learn from my mistake.
Some credit goes to Joey Sochacki as I did use and modify some of his regular expression.

Validate email addresses

This is only basic email validation. Not recommended to use. Validate perfect email format using regex is not really efficient.

$email = "test@example.com";
if (preg_match('/^[^0-9][a-zA-Z0-9_]+([.][a-zA-Z0-9_]+)*[@][a-zA-Z0-9_]+([.][a-zA-Z0-9_]+)*[.][a-zA-Z]{2,4}$/',$email)) {
    echo "Your email is ok.";
} else {
    echo "Wrong email address format";
}

A better solution for validate email syntax is using filter_var. Thanks to cx42net for pointing me out to filter_var.

if (filter_var('test+email@fexample.com', FILTER_VALIDATE_EMAIL)) {
    echo "Your email is ok.";
} else {
    echo "Wrong email address format.";
}

Validate usernames
Validate username, consist of alpha-numeric (a-z, A-Z, 0-9), underscores, and has minimum 5 character and maximum 20 character. You could change the minimum character and maximum character to any number you like.
```
$username = "user_name12";
if (preg_match('/^[a-z\d_]{5,20}$/i', $username)) {
    echo "Your username is ok.";
} else {
    echo "Wrong username format.";
}
```

Validate telephone numbers

Validate US phone number

$phone = "(021)423-2323";
if (preg_match('/\(?\d{3}\)?[-\s.]?\d{3}[-\s.]\d{4}/x', $phone)) {
    echo "Your phone number is ok.";
} else {
    echo "Wrong phone number.";
}

Validate IP addresses

$IP = "198.168.1.78";
if (preg_match('/^(([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]).){3}([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$/',$IP)) {
    echo "Your IP address is ok.";
} else {
    echo "Wrong IP address.";
}

Validate postal codes

Validate US Postal codes

$zipcode = "12345-5434";
if (preg_match("/^([0-9]{5})(-[0-9]{4})?$/i",$zipcode)) {
    echo "Your Zip code is ok.";
} else {
    echo "Wrong Zip code.";
}

Validate SSN

Validate US Sosial Security Number

$ssn = "333-23-2329";
if (preg_match('/^[\d]{3}-[\d]{2}-[\d]{4}$/',$ssn)) {
    echo "Your SSN is ok.";
} else {
    echo "Wrong SSN.";
}

Validate credit card

$cc = "378282246310005";
if (preg_match('/^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6011[0-9]{12}|3(?:0[0-5]|[68][0-9])[0-9]{11}|3[47][0-9]{13})$/', $cc)) {
    echo "Your credit card number is ok.";
} else {
    echo "Wrong credit card number.";
}

Validate domain

$url = "http://komunitasweb.com/";
if (preg_match('/^(http|https|ftp):\/\/([A-Z0-9][A-Z0-9_-]*(?:\.[A-Z0-9][A-Z0-9_-]*)+):?(\d+)?\/?/i', $url)) {
    echo "Your url is ok.";
} else {
    echo "Wrong url.";
}

Extract domain name from certain URL

$url = "http://komunitasweb.com/index.html";
preg_match('@^(?:http://)?([^/]+)@i', $url, $matches);
$host = $matches[1];
 
echo $host;

Highlight a word in the content

$text = "Sample sentence from KomunitasWeb, regex has become popular in web programming. Now we learn regex. According to wikipedia, Regular expressions (abbreviated as regex or regexp, with plural forms regexes, regexps, or regexen) are written in a formal language that can be interpreted by a regular expression processor";
 
$text = preg_replace("/\b(regex)\b/i", '<span style="background:#5fc9f6">\1</span>', $text);
 
echo $text;

Please note that some of this regex recipe doesn’t really validate to all conditions, therefore not a perfect solution, but it will cover most of the case. It’s not really worth to build perfect validation to all case, and waste your time in the process. Well that just my opinion. Feel free to share your regex magic and your opinion.

PHP Regular Expressions