php语法如何利用str_replace和strip_tags去掉连续空格

<?php
  $note = strip_tags($value['Content']);
  $note = trim($note);
  $note = str_replace(" ","",$note);
  $note = preg_replace('#\s+#', ' ',trim($note));
  $note = str_replace("<","<",$note);
  $note = str_replace(">",">",$note);
  $note = preg_replace("/[ ]{1,}/isu"," ",$note);
  echo getsubstr($note,100);
?>