Because making a truly correct email validation function is harder than one may think, consider using this one which comes with PHP through the filter_var function (http://www.php.net/manual/en/function.filter-var.php):

<?php
$email = "someone@domain .local";

if(!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo "E-mail is not valid";
} else {
    echo "E-mail is valid";
}
?>