<?php

$string = "<strong>Blabla1</strong> Blaabla2<br /> Blaabla3 <strong>Blaabla4</strong> Blaabla5 Blaabla6<br /><br /> Blaabla7 <span style='color:#B22222;'>Blaabla8</span> Blaabla9";
var_dump(preg_split('~(?:</?[a-zA-Z0-9][^>]*+>|\S)++\K|\s~',$string,null,PREG_SPLIT_NO_EMPTY));

?>