Saving to a file in PHP - php

Question

I have to save unique passwords and usernames to a file, but my code duplicate the first two entries, then start working properly from there. here's my code. What am I missing? I using Mac with MAMP. I'm testing the code using curl with this command curl -d login=tenten -d passwd=peter -d submit=OK 'http://localhost:8080/php/create.php'
function user_exist($user_array, $user_name)
{
foreach ($user_array as $user) {
if ($user['login'] === $user_name)
return (TRUE);
}
return (FALSE);
}
if ($_POST['submit'] === 'OK')
{
if ($_POST['passwd'] != "" && $_POST['login'] != "")
{
create_file('../private');
if (file_exists('../private/passwd'))
{
$hash_passwd = hash('whirlpool', $_POST['passwd']);
$passwds = unserialize(file_get_contents('../private/passwd'));
if (!user_exist($passwds, $_POST['login']))
{
$passwds[] = array('login' => $_POST['login'], 'passwd' => $hash_passwd);
$serialize = serialize($passwds);
file_put_contents('../private/passwd', $serialize);
echo "OK\n";
}
else
{
echo "ERROR\n";
}
}
else
{
$hash_passwd = hash('whirlpool', $_POST['passwd']);
$user_cred = array('login' => $_POST['login'], 'passwd' => $hash_passwd);
$serialize = serialize($user_cred);
file_put_contents('../private/passwd', $serialize);
echo "OK\n";
}
}
else
{
echo "ERROR\n";
}
}
else
{
echo "ERROR\n";
}