delete unknown characters from my form data?

I want function

Delete all this characters from my forms

!@#$%^&*()-_+~`'";\|][/.,~

Only accept English characters linke (abcdefgh ....)

to use it in my registration form

$text = "something$^£^£$&£";
$text= preg_replace('/[^\w\d_ -]/si', '', $text);
echo $text; // output something

Have a look at inbuilt PHP functions :

http://www.php.net/manual/en/function.filter-input.php

You can use :jQuery plugin: Validation.

It's powerful