This post will show you how to strip everything from a string except alphanumeric characters to create a post-slug.
First, I'll demonstrate it is what the code will accomplish. Consider the following string of text:
What we're doing in this post is essentially creating a post-slug that looks something like this: h3-110-w-0rld or, using a second function, this: h3110-w0rld.
The Method
Using PHP's preg_replace() 
function:
The output is as follows:
Note the three white spaces between h3110 and w0RlD? We can remove them with another regular expression search and replace. This expression will replace multiple white spaces with a single space:
The last thing we do is make the string lower case and replace the single white spaces with a hyphen.
PHP Functions
If we create a function from the above, it'll look like this:
Example
Output is:
You'll note that there's an awful lot of hyphens separating text. A more effective means of creating a slug might be to:
- Make string lower case.
- Strip the string of anything other than letters, numbers, multiple spaces and multiple hyphens.
- Replace multiple white spaces and multiple hyphens with a single hyphen.
That function looks like this:
Example
Output is h3110-w0rld
See also: Create Post Slugs.
