php验证邮箱正确性

<?php
function validateEmailFormat($email) {
    if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
        return true;
    } else {
        return false;
    }
}

$email = "example@example.com";
if (validateEmailFormat($email)) {
    echo "邮箱格式正确";
} else {
    echo "邮箱格式不正确";
}
?>

<?php
function validateEmailExistence($email) {
    $domain = substr(strrchr($email, "@"), 1);
    if (!checkdnsrr($domain, "MX")) {
        return false;
    }

    $port = 25;
    $timeout = 10;
    $socket = fsockopen($domain, $port, $errno, $errstr, $timeout);

    if (!$socket) {
        return false;
    }

    $hello = "HELO " . $domain . "\r\n";
    $mailFrom = "MAIL FROM:<" . "noreply@example.com" . ">\r\n";
    $rcptTo = "RCPT TO:<" . $email . ">\r\n";
    $quit = "QUIT\r\n";

    fwrite($socket, $hello);
    fwrite($socket, $mailFrom);
    fwrite($socket, $rcptTo);
    fwrite($socket, $quit);

    $response = fgets($socket, 1024);
    fclose($socket);

    if (strpos($response, "250") === 0 || strpos($response, "251") === 0) {
        return true;
    } else {
        return false;
    }
}

$email = "example@example.com";
if (validateEmailExistence($email)) {
    echo "邮箱存在";
} else {
    echo "邮箱不存在";
}
?>