Delete an existing namespace.
string $prefix The namespace prefix (eg 'foaf'):
public static function delete($prefix) {
if (!is_string($prefix) or $prefix === null or $prefix === '') {
throw new InvalidArgumentException("\$prefix should be a string and cannot be null or empty");
}
$prefix = strtolower($prefix);
if (isset(self::$namespaces[$prefix])) {
unset(self::$namespaces[$prefix]);
}
}