In answer to the question in how to write to a file in PHP you can use the following as an example:
$fp = fopen ($filename, "a"); # a = append to the file. w = write to the file (create new if doesn't exist)
if ($fp) {
fwrite ($fp, $text); //$text is what you are writing to the file
fclose ($fp);
$writeSuccess = "Yes";
#echo ("File written");
}
else {
$writeSuccess = "No";
#echo ("File was not written");
}