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
    Conquering Impostor Syndrome

    Two years ago I documented my struggles with Imposter Syndrome and the response was immense.  I received messages of support and commiseration from new web developers, veteran engineers, and even persons of all experience levels in other professions.  I've even caught myself reading the post...

  • By
    fetch API

    One of the worst kept secrets about AJAX on the web is that the underlying API for it, XMLHttpRequest, wasn't really made for what we've been using it for.  We've done well to create elegant APIs around XHR but we know we can do better.  Our effort to...

Incredible Demos

  • By
    MooTools Equal Heights Plugin:  Equalizer

    Keeping equal heights between elements within the same container can be hugely important for the sake of a pretty page. Unfortunately sometimes keeping columns the same height can't be done with CSS -- you need a little help from your JavaScript friends. Well...now you're...

  • By
    CSS Sprites

    The idea of CSS sprites is pretty genius. For those of you who don't know the idea of a sprite, a sprite is basically multiple graphics compiled into one image. The advantages of using sprites are: Fewer images for the browser to download, which means...

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!