admin,password
user1,password
user1,password
....,......

<? session_start();

if(!isset($_POST[Submit]))
{

initial content into form
$fc=file("../username/member.txt");
$userid_no = $_GET['record_id'];
$line = split("\|",$fc[$userid_no]);
$user_id = $line[0];
$password = $line[1];
$firstname = $line[2];
$lastname = $line[3];
$email = $line[4];

}
else
{
if(isset($_GET['record_id']))
{

$update = $_POST['user_id'];
$update .= "|";
$update .= $_POST['password'];
$update .= "|";
$update .= $_POST['lastname'];
$update .= "|";
$update .= $_POST['firstname'];
$update .= "|";
$update .= $_POST['email'];
$update .= "|";
$update .= "";
$update .= "|";
$update .= "2";

$contents=file("../username/member.txt");
$fileName = "member.txt";
$edit_line = $_GET['record_id'];
$replace_text =$update;


for($c = 0; $c < count($contents)-1; $c++)
{
$contents[$c] = str_replace( "\n", "", $contents[$c] );

}

$contents[$edit_line] = $replace_text;

if (!$fp = fopen($fileName,"w")) { die("Cannot open file"); }

$count = 0;
foreach ($contents as $edit_line)
{


if($count != $_GET['record_id']){
$str="\n".$contents[$edit_line];
fwrite($fp,$str);
}
$count++;


}
fclose($fp);

}
}

?>

....
fopen($fileName,"w")
....