PHP highlight search keywords

function highlightkeyword($str, $search) {
 if($search){
  $highlightcolor = "#FFCC33";
  $occurrences = substr_count(strtolower($str), strtolower($search));
  $newstring = $str;
  $match = array();
 
  for ($i=0;$i<$occurrences;$i++) {
   $match[$i] = stripos($str, $search, $i);
   $match[$i] = substr($str, $match[$i], strlen($search));
   $newstring = str_replace($match[$i], '[#]'.$match[$i].'[@]', strip_tags($newstring));
  }
 
  $newstring = str_replace('[#]', '<span style="background-color:'.$highlightcolor.'">', $newstring);
  $newstring = str_replace('[@]', '</span>', $newstring);
  return $newstring;
 }else{
  return $str;
 }
}

Credit: http://www.webdevdoor.com/php/highlight-search-keyword-string-function/