url_title()

url_title($str, $separator = '-', $lowercase = FALSE)

Takes a string as input and creates a human-friendly URL string. This is useful if, for example, you have a blog in which you’d like to use the title of your entries in the URL. Example:

$title = "What's wrong with CSS?";
$url_title = url_title($title);
// Produces: Whats-wrong-with-CSS

The second parameter determines the word delimiter. By default dashes are used. Preferred options are: - (dash) or _ (underscore)

Example:

$title = "What's wrong with CSS?";
$url_title = url_title($title, 'underscore');
// Produces: Whats_wrong_with_CSS

The third parameter determines whether or not lowercase characters are forced. By default they are not. Options are boolean TRUE/FALSE.

Example:

$title = "What's wrong with CSS?";
$url_title = url_title($title, 'underscore', TRUE);
// Produces: whats_wrong_with_css