strange, yet probably obvious php error

Okay, this is my first post, so bear with me. I am coding a blog-type site, and I'm trying to filter out some HTML tags from files. I'm using the callback of the filter_var() function. I get a:

Fatal error: Call to undefined function filter_var() in /home/benjamin/public_html/homeofben/blogview.php on line 18

I don't know why the function wouldn't exist, as I am using PHP 5 and www.w3schools.com says the filter_var() function exists in PHP 5. However, I have a feeling this is an obvious thing. Help would be appreciated.

why not just use htmlentities() ?

only_samurai wrote: why not just use htmlentities() ?

That's the best way to do it ^^

Uber0n wrote: [quote]only_samurai wrote: why not just use htmlentities() ?

That's the best way to do it ^¹

What has everyone against htmlspecialchars function?

Oh, I figured out how to do it with strip_tags(). Thanks anyway.