Match Special Letters with PHP Regular Expressions

By  on  

Regular expressions come with all sorts of peculiarities, one of which I recently ran into when creating a regex within PHP and preg_match.  I was trying to parse strings with the format "Real Name (:username)" when I ran into a problem I would see a lot at Mozilla:  my regular expression wasn't properly catching "special" or "international" letters, like à, é, ü, and the dozens of others.

My regular expression was using A-z in the real name matching piece of the regex, which I assumed would match special letters, but it did not:

preg_match(
  "/([A-Za-z -]+)?\s?\[?\(?:([A-Za-z0-9\-\_]+)\)?\]?/", 
  "Yep Nopé [:ynope]", $matches);

// 0 => '[:ynope]', 1 => 'Yep Nopé', 2 => 'ynope'

To match international letters, I needed to update my regular expression in two ways:

  • Change A-z to \pL within the matching piece
  • Add the u modifier makes the string treated as UTF-8

The updated regex would be:

preg_match(
  "/([\pL -]+)?\s?\[?\(?:([\pL0-9\-\_]+)\)?\]?/u", 
  "Yep Nopé [:ynope]", $matches);

// 0 => 'Yep Nopé [:ynope]', 1 => 'Yep Nopé', 2 => 'ynope'

You can see my simple test bed here. If you're afraid that other characters might seep in, or don't trust \pL, you could list every special letter manually (i.e. [A-zàáâä....])

One of the nice parts of working at a truly global organization like Mozilla is that I'm exposed to many edge cases; in this case, a few special letters!

Recent Features

  • By
    Convert XML to JSON with JavaScript

    If you follow me on Twitter, you know that I've been working on a super top secret mobile application using Appcelerator Titanium.  The experience has been great:  using JavaScript to create easy to write, easy to test, native mobile apps has been fun.  My...

  • By
    Page Visibility API

    One event that's always been lacking within the document is a signal for when the user is looking at a given tab, or another tab. When does the user switch off our site to look at something else? When do they come back?

Incredible Demos

  • By
    Introducing MooTools ScrollSide

    This post is a proof of concept post -- the functionality is yet to be perfected. Picture this: you've found yourself on a website that uses horizontal scrolling instead of vertical scrolling. It's an artistic site so you accept that the site scrolls left to right.

  • By
    Create Spinning Rays with CSS3 Animations & JavaScript

    Thomas Fuchs, creator of script2 (scriptaculous' second iteration) and Zepto.js (mobile JavaScript framework), creates outstanding animated elements with JavaScript.  He's a legend in his own right, and for good reason:  his work has helped to inspire developers everywhere to drop Flash and opt...

Discussion

  1. [A-z] doesn’t do what you seem to quite what you think it does. That character range includes the characters in the ASCII table between Z and a: [\]^_. It looks like you should be using [A-Za-z].

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!