如何在字符串页面的字符串中阻止HTML代码

i've got i little question. i'm trying to block all html code for my profile page for my website, so people cant break the whole system, and mostly so they cant put url's in their profile quote this is my code

function block_html($string) {
  $find = '/\<(.*?)\>/';
  $replace = '';
  return preg_replace($find,$replace,$str);
}

thanks already