ASPit - Totally ASP JSit - Totally JavaScript
Search PHPit

Use this textbox to search for articles on PHPit. Seperate keywords with a space.


Mastering Regular Expressions in PHP

(Page 2 out of 4)

What would a good tutorial be without some real examples? Let's first have a look at a simple e-mail validation function. An e-mail address must start with letters or numbers, then have a @, then a domain, ending with an extension. The regex for that would be something like this: ^[a-zA-Z0-9_\.\-]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-\.]+$

Let me quickly explain that regex. Basically, the first part says that it must all be letters or numbers. Then we get the @, and after that there should be letters and/or numbers again (the domain). Finally we check for a period, and then for an extension. The code to use this regex looks like this:

// Good e-mail
$good = "[email protected]";

// Bad e-mail
$bad = "blabla@blabla";

// Let's check the good e-mail
if (preg_match("/^[a-zA-Z0-9_\.\-]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-\.]+$/", $good)) {
        echo "Valid e-mail";
} else {
        echo "Invalid e-mail";

echo '';

// And check the bad e-mail
if (preg_match("/^[a-zA-Z0-9_\.\-]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-\.]+$/", $bad)) {
        echo "Valid e-mail";
} else {
        echo "Invalid e-mail";


The result of this would be "Valid E-mail. Invalid E-mail", of course. We have just checked if an e-mail address is valid. If you wrap the above code in a function, you've got yourself a e-mail validation function. Keep in mind though that the regex isn't perfect: after all, it doesn't check whether the extension is too long, does it? Because I want to keep this tutorial short, I won't give the full fledged regex, but you can find it easily via Google.

« Previous: What are Regular Expressions?
Next: Another Example »

Leave a Reply

About the author
Dennis Pallett is the main contributor to PHPit. He owns several websites, including ASPit and Chill2Music. He is currently still studying.
Article Index
  1. What are Regular Expressions?
  2. An Example
  3. Another Example
  4. What exactly is possible with Regular Expressions?
Bookmark Article
Download Article
Download this article as a PDF file