Slugs for SEO using PHP - Appending name to end of URL - php

Question

Something I have noticed on the StackOverflow website:
If you visit the URL of a question on StackOverflow.com:
"https://stackoverflow.com/questions/10721603"
The website adds the name of the question to the end of the URL, so it turns into:
"https://stackoverflow.com/questions/10721603/grid-background-image-using-imagebrush"
This is great, I understand that this makes the URL more meaningful and is probably good as a technique for SEO.
What I wanted to Achieve after seeing this Implementation on StackOverflow
I wish to implement the same thing with my website. I am happy using a header() 301 redirect in order to achieve this, but I am attempting to come up with a tight script that will do the trick.
My Code so Far
Please see it working by clicking here
// Set the title of the page article (This could be from the database). Trimming any spaces either side
$original_name = trim(' How to get file creation & modification date/times in Python with-dash?');
// Replace any characters that are not A-Za-z0-9 or a dash with a space
$replace_strange_characters = preg_replace('/[^\da-z-]/i', " ", $original_name);
// Replace any spaces (or multiple spaces) with a single dash to make it URL friendly
$replace_spaces = preg_replace("/([ ]{1,})/", "-", $replace_strange_characters);
// Remove any trailing slashes
$removed_dashes = preg_replace("/^([\-]{0,})|([\-]{2,})|([\-]{0,})$/", "", $replace_spaces);
// Show the finished name on the screen
print_r($removed_dashes);
The Problem
I have created this code and it works fine by the looks of things, it makes the string URL friendly and readable to the human eye. However, it I would like to see if it is possible to simplify or "tightened it up" a bit... as I feel my code is probably over complicated.
It is not so much that I want it put onto one line, because I could do that by nesting the functions into one another, but I feel that there might be an overall simpler way of achieving it - I am looking for ideas.
In summary, the code achieves the following:
Removes any "strange" characters and replaces them with a space
Replaces any spaces with a dash to make it URL friendly
Returns a string without any spaces, with words separated with dashes and has no trailing spaces or dashes
String is readable (Doesn't contain percentage signs and + symbols like simply using urlencode()
Thanks for your help!
Potential Solutions
I found out whilst writing this that article, that I am looking for what is known as a URL 'slug' and they are indeed useful for SEO.
I found this library on Google code which appears to work well in the first instance.
There is also a notable question on this on SO which can be found here, which has other examples.

Answer 1

I tried to play with preg like you did. However it gets more and more complicated when you start looking at foreign languages.
What I ended up doing was simply trimming the title, and using urlencode
$url_slug = urlencode($title);
Also I had to add those:
$title = str_replace('/','',$title); //Apache doesn't like this character even encoded
$title = str_replace('\\','',$title); //Apache doesn't like this character even encoded
There are also 3rd party libraries such as: http://cubiq.org/the-perfect-php-clean-url-generator

Answer 2

Indeed, you can do that:
$original_name = ' How to get file creation & modification date/times in Python with-dash?';
$result = preg_replace('~[^a-z0-9]++~i', '-', $original_name);
$result = trim($result, '-');
To deal with other alphabets you can use this pattern instead:
~\P{Xan}++~u
or
~[^\pL\pN]++~u