look at your source code. When you echo it, you'll see the results properly written on new lines
string1 part a
string1 part b
string1 part c
but, as you know, html doesn't care about newlines, if you want a newline to appear on the browser, you have to use a break. That means, yo'ud have to convert all your newlines to breaks. PHP has a handy little function called nl2br()
echo nl2br($string);
Cgraz