/**
* Generates a URN(Uniform Resource Name) for the given title to uniquely identify a subject(eg: in seo friendly urls)
* @return mixed boolean false if can't generate a urn, otherwise a string with the urn
*/
public function generateUrn($title)
{
//Translate the text to english as all urns should be english
if ($translated = SiteLibrary::translate($title)) {
$title = $translated;
}
//then lets generate a clean title(just numbers and letters, remove everything else)
$clean_title = ereg_replace("[^A-Za-z0-9 ]", "", $title);
$clean_title = strtolower($clean_title);
$clean_title = preg_replace('/\\s+/', ' ', $clean_title);
//replace any sequence of whitespace greater than one, with only one
$clean_title = trim($clean_title);
//And replace whitespaces with dashes(this gives us the possible urn)
$possible_urn = str_replace(" ", "-", $clean_title);
//Verify that the obtained possible_urn its really unique on the database table
//if not, generate one adding a sequence number to the possible_urn variable
//Make 50 attempts to find a unique urn
for ($i = 1; $i <= 50; $i++) {
$possible_urn_i = $i == 1 ? $possible_urn : $possible_urn . '_' . $i;
if (!Subject::model()->find('urn=:urn', array(':urn' => $possible_urn_i))) {
$urn = $possible_urn_i;
//we found it
return $urn;
}
}
return false;
}
