在php中验证后，recaptcha不发送电子邮件

<?php
// 验证reCAPTCHA
$recaptchaResponse = $_POST['g-recaptcha-response'];
$secretKey = 'YOUR_RECAPTCHA_SECRET_KEY';
$verifyResponse = file_get_contents('https://www.google.com/recaptcha/api/siteverify?secret=' . $secretKey . '&response=' . $recaptchaResponse);
$responseData = json_decode($verifyResponse);

if ($responseData->success) {
    // reCAPTCHA验证成功，发送电子邮件
    $to = 'recipient@example.com';
    $subject = 'Hello';
    $message = 'This is a test email.';
    $headers = 'From: sender@example.com' . "\r\n" .
        'Reply-To: sender@example.com' . "\r\n" .
        'X-Mailer: PHP/' . phpversion();

    if (mail($to, $subject, $message, $headers)) {
        echo 'Email sent successfully.';
    } else {
        echo 'Failed to send email.';
    }
} else {
    // reCAPTCHA验证失败
    echo 'reCAPTCHA verification failed.';
}
?>