upcase split

var_dump(ucsplit('MyString'));
// array(2) {
//   [0]=>
//   string(2) "My"
//   [1]=>
//   string(6) "String"
// }

/**
* Split a string into pieces by uppercase characters.
*
* @param  string  $string
* @return array
*/
function ucsplit($string)
{
  return preg_split('/(?=\p{Lu})/u', $string, -1, PREG_SPLIT_NO_EMPTY);
}