textbox: disallow html input

[campbem]

Using any *very* compatible scripting (javascript,php, etc) what would be the easiest way to completely disallow html input from being entered into an html form?

 

I do not want to strip html tags, or re-encode them for a database, or allow only certain tags...I want the textbox to throw away the entire form if any html tag is entered from any source.

 

I suppose I could regex or use some part of an existing php function to detect tags, but I don't think I could account for  all possible tags - I basically want the textbox to be TRULY text only. I'd probably want to allow someone to use <> and other english language characters as they would in an actual english sentence, but I want the form to just deny any programming tags.

 

Does any one know of snippets out there that already do this? Thanks!

[RichardRotterdam]

you can't restrict them from entering html tags but you can filter the html out when you submit a form. Using javascript might seem like a solution to prevent a person from entering html into a textarea but you can always disable javascript

[soycharliente]

<?php
$post = nl2br(htmlentities($r["post"], ENT_QUOTES));
?>

 

I pull data from a db with that. It converts the data to the HTML entities (like < to <) so that it will render everything exactly as they typed in.