A Simple PHP Class to Back Up MySQL

My web host is cutting over from allowing shell scripts to requiring scripting languages instead. I had wanted to write a script in PHP, so I figured this is a good opportunity.
Here is a simple PHP class to back up a MySQL database and blanket-delete old backups from a directory.

class MysqlBackup {
    private $host = 'host';
    private $db = 'db';
    private $user = 'user';
    private $passwd = 'passwd';
    private $dest_dir = 'dest_dir';
    private $dest_file_prefix = 'dest_file_prefix';
    private $days_to_keep = '0';
public function __construct($host, $db, $user, $passwd, $dest_dir, $dest_file_prefix, $days_to_keep) {
        $this->host = $host;
        $this->db  = $db;
        $this->user  = $user;
        $this->passwd  = $passwd;
        $this->dest_dir = $dest_dir;
        $this->dest_file_prefix = $dest_file_prefix;
        $this->days_to_keep = $days_to_keep;
    }
public function dump() {
        print "MysqlBackup::dump()\n";
        print "Dumping database: $this->db\n";
        $date = date('m-d-Y_H-i-s');
        print "Dump file date: $date\n";
        $dest_file = $this->dest_file_prefix . '.' . $date . '.sql.bz2';
        $dest_file_path = "$this->dest_dir/$dest_file\n";
        print "Dump file destination: $dest_file_path";
        $cmd = "mysqldump --add-drop-table --host=$this->host --user=$this->user --password=$this->passwd $this->db | bzip2 -c > $dest_file_path";
        // call 'system' with '$cmd' as an argument here
        // for some reason, WordPress wants to blow up when I include the call
    }
public function clean() {
        print "MysqlBackup::clean()\n";
        $handle = opendir($this->dest_dir) or die ('Could not open directory: '. $this->dest_dir);
        print 'Opened directory: ' . $this->dest_dir . "\n";
        print "Examining files\n";
        $keep_threshold_time = strtotime("-$this->days_to_keep days");
        while (false !== ($file = readdir($handle))) {
            $dest_file_path = "$this->dest_dir/$file";
            print "'$dest_file_path': ";
            if(!is_dir($dest_file_path)) {
                $file_time = filemtime($dest_file_path);
                print "$file_time < $keep_threshold_time? ";
                if($file_time < $keep_threshold_time) {
                    print "Yes. Deleting.\n";
                    unlink($dest_file_path);
                }
                else {
                    print "No. Skipping.\n";
                }
            }
            else {
                print "A Directory, excluding\n";
            }
        }
    }
}