Allow Spaces but not other random characters?

[eluser]Jelmer[/eluser]
Something like this:

Code:

function check_blog_name( $str )
{
    return ( preg_match( '/[^a-z0-9 ]/i', $str ) === 0 );
}

EDIT: that matches anything but a to z, 0 to 9 or spaces (the "i" at the end makes it not care about upper/lowercase), if it finds more then 0 matches that means there are disallowed characters.