PHP code to generate safe URL?

Question

We need to generate a unique URL from the title of a book - where the title can contain any character. How can we search-replace all the 'invalid' characters so that a valid and neat lookoing URL is generated?

For instance:

"The Great Book of PHP"

www.mysite.com/book/12345/the-great-book-of-php

"The Greatest !@#$ Book of PHP"

www.mysite.com/book/12345/the-greatest-book-of-php

"Funny title     "

www.mysite.com/book/12345/funny-title

Answer 1

Ah, slugification

// This function expects the input to be UTF-8 encoded.
function slugify($text)
{
    // Swap out Non "Letters" with a -
    $text = preg_replace('/[^\\pL\d]+/u', '-', $text); 

    // Trim out extra -'s
    $text = trim($text, '-');

    // Convert letters that we have left to the closest ASCII representation
    $text = iconv('utf-8', 'us-ascii//TRANSLIT', $text);

    // Make text lowercase
    $text = strtolower($text);

    // Strip out anything we haven't been able to convert
    $text = preg_replace('/[^-\w]+/', '', $text);

    return $text;
}

This works fairly well, as it first uses the unicode properties of each character to determine if it's a letter (or \d against a number) - then it converts those that aren't to -'s - then it transliterates to ascii, does another replacement for anything else, and then cleans up after itself. (Fabrik's test returns "arvizturo-tukorfurogep")

I also tend to add in a list of stop words - so that those are removed from the slug. "the" "of" "or" "a", etc (but don't do it on length, or you strip out stuff like "php")