running preg_split("\s|\b/u", "I search 1, regex (regular expression) to: That's it is! Und über den Wolken müssen wir...", -1, PREG_SPLIT_NO_EMPTY)

array (
  0 => 'I',
  1 => 'search',
  2 => '1',
  3 => ',',
  4 => 'regex',
  5 => '(',
  6 => 'regular',
  7 => 'expression',
  8 => ')',
  9 => 'to',
  10 => ':',
  11 => 'That',
  12 => '\'',
  13 => 's',
  14 => 'it',
  15 => 'is',
  16 => '!',
  17 => 'Und',
  18 => 'über',
  19 => 'den',
  20 => 'Wolken',
  21 => 'müssen',
  22 => 'wir',
  23 => '...',
)