How can you convert a string that contains your first and last name and sometimes middle name into an array with this format?
customFunction('Chris Morris');
// array('firstname' => 'Chris', 'lastname' => 'Morris')
customFunction('Chris D. Morris');
// array('firstname' => 'Chris D.', 'lastname' => 'Morris')
customFunction('Chris');
// array('firstname' => 'Chris', 'lastname' => '')