I think silviuks, is right, you not using $bg as background color (you just set its value).

hi, there's a mistake in my earlier code
here's the right one ( i've tried it)
first u must make a hidden field in your form for number of textbox
example "<input name="textbox_num" type="hidden"...

try it like this

for($i=0;$<$number_of_textboxes;$i++){
$txtboxname = $txt.$i;
$textbox_value .= $_POST[$txtboxname] ;
$textbox_value .= "<br>"; //one value per line
}
...

hi dan maybe u can check php.net theres a good resources to learn it, and u can download php manual there ....