PHP query CSV

i have a script i just made for you but i have to ask if you need me to add email validation to it. also, does it need to have input fields for the first name column?

here it is:

<form action="csv.php" method="post">
<p>Email:<input type="text" name="email" /></p>
<p>Name:<input type="text" name="name" /></p>
<p><input type="submit" name="submit" value="Submit" /></p>
</form>
<?php
if (isset($_POST['submit'])) {
function check($fieldname)
{
if(!preg_match("/[^a-zA-Z0-9\.\-\Ä\ä\Ö\ö\Ü\ü\@\ ]+$/s",$fieldname)) {
return TRUE;
}
else {
return FALSE;
}
}
$email = $_REQUEST['email'];
$name = $_REQUEST['name'];
$error = 0;
if ($email == NULL) {
$error_msg .= "Email field is not filled out\\n\\n";
$error++;
}
if (!$email == NULL && !check($email)) {
$error_msg .= "Email field contains illegal characters\\n\\n";
$error++;
}
if ($name == NULL) {
$error_msg .= "Name field is not filled out\\n\\n";
$error++;
}
if (!$name == NULL && !check($name)) {
$error_msg .= "Name field contains illegal characters\\n\\n";
$error++;
}
if ($error > 0) {
$error_msg .= "There currently are " . $error . " errors";
echo '<script type="text/javascript">alert ("' . $error_msg . '");</script>';
}
if ($error == 0) {
$row = 1;
$open = fopen("file.csv", "r");
while (($data = fgetcsv($open, 1000, ",")) !== FALSE) {
if ($data[0] == $email) {
die('email already exists');
}
}
fclose($open);
$csv = $email . ", " . $name . "\n";
$open = fopen("file.csv", "a");
$write = fwrite($open, $csv);
fclose($open);
}
}
?>