Just use regular HTML, and point the form action to the script that processes it.
<FORM METHOD=POST ACTION="<?php echo $PHP_SELF?>">
<INPUT TYPE=text NAME=myvar VALUE=''>
<INPUT TYPE=submit VALUE='Submit'>
</FORM>
This assumes the processing is dome on the same page as the form is located. When they click submit, you can get he variables by using
if ($HTTP_POST_VARS){
extract($HTTP_POST_VARS);
}
Now you can access $myvar and proccess it.