Samme tjek i PHP og JavaScript

Tjekker disse koder det samme i henholdsvis PHP og JavaScript? Det er specielt tjekningen af e-mail jeg er i tvivl om!

JavaScript-------------------------

function check_input() {
if (!(document.register.username.value.length >= 3 && document.register.username.value.length <= 20 && document.register.username.value.match(/^[a-z0-9_-]+$/i))) {
alert('Please specify a valid username!');
document.register.username.focus();
return false; }

if (!(document.register.password.value.length >= 6 && document.register.username.value.length <= 20)) {
alert('Please specify a valid password!');
document.register.password.focus();
return false; }

if (!(document.register.email.value.indexOf('@') > 0 && document.register.email.value.lastIndexOf('.') > document.register.email.value.lastIndexOf('@') && document.register.email.value.indexOf('@') == document.register.email.value.lastIndexOf('@')) || (document.register.email.value.indexOf('@.')) > 0 || (document.register.email.value.indexOf(';')) > 0 || (document.register.email.value.indexOf(' ')) > 0 || (document.register.email.value.indexOf(':')) > 0 || (document.register.email.value.indexOf(',')) > 0 || (document.register.email.value.indexOf('.@')) > 0  ) {
alert('Please specify a valid e-mail!');
document.register.email.focus();
return false; }

if (!(document.register.country.value > 0)) {
alert('Please specify a valid country!');
document.register.country.focus();
return false; }

if (!(document.register.gender.value > 0)) {
alert('Please specify a valid gender!');
document.register.gender.focus();
return false; }

if (!(document.register.age.value > 0)) {
alert('Please specify a valid age!');
document.register.age.focus();
return false; }

if (!(document.register.password.value == document.register.password_check.value)) {
alert('Your password entries did not match!');
document.register.password_check.focus();
return false; }

document.register.submit(); }

PHP -----------------------------

if (!eregi('^[a-z0-9_-]{3,20}$', $_POST['username'])) {
header("location:register.php?status=invalid_username");
} elseif (!eregi('.{6,20}', $_POST['password'])) {
header("location:register.php?status=invalid_password");
} elseif (!eregi('.@.+.',$_POST['email'])) {
header("location:register.php?status=invalid_email");
} elseif ($_POST['country'] < 0) {
header("location:register.php?status=invalid_country");
} elseif ($_POST['gender'] < 0) {
header("location:register.php?status=invalid_gender");
} elseif ($_POST['age'] < 0) {
header("location:register.php?status=invalid_age");
} elseif ($_POST['password'] != $_POST['password_check']) {
header("location:register.php?status=invalid_password_check");