Help storing to a Txt file PHP

Hi can any one help

i have 4 txt boxes which load 4 prices from a txt file that works ok.
if the user then changes the price in the box and hits a button:-

on (release) {
time = new Date();
url = “./store.php?time=”+time.getTime()+"&post="+escape(post)+"&post2="+escape(post2)+"&post3="+escape(post3)+"&post4="+escape(post4);
loadVariablesNum (url, 0);
}

i want it to save the text to the txt file

store.php has this code in it:-

<?
// store the variables passed by POST
$fp = fopen(“data.txt”, “w”);
if (!$fp) die (“cannot open the file”);
fputs($fp, “&post1=”.$post1, 4096);
fputs($fp, “&post2=”.$post2, 4096);
fputs($fp, “&post3=”.$post3, 4096);
fputs($fp, “&post4=”.$post4, 4096);
fclose($fp);
?>

i cant get it to work?? any ideas