reCAPTCHA PHP集成但未验证

This is my first time posting on stackoverflow. I am Designer teaching myself HTML5, CSS, Javascript & PHP. I have a very basic grasp on Javascript & PHP with more experience in HTML5 & CSS. I have been researching my issue and attempting to fix this for several weeks (when time is available) and keep coming up short. Here is my issue:

I have been working on a website with two forms. I have gone to reCAPTCHA grabbed my public & private keys and added them to my website and my reCAPTCHA is displayed on the site.

Currently, someone can enter in the reCAPTHCA correctly (or incorrectly) and the form will still submit. This is only because I have removed the else { } code in the validating php file, see below. When I add the else { } code the form will die on submit and give me "The reCAPTCHA was entered incorrectly. Go back and try it again.(reCAPTCHA said: incorrect-captcha-sol)". The code below is placed directly below my opening < ?php tag.

require_once('recaptchalib.php');
$privatekey = "myprivatekey_removed";
$resp = recaptcha_check_answer ($privatekey,
                $_SERVER["REMOTE_ADDR"],
                $_POST["recaptcha_challenge_field"],
                $_POST["recaptcha_response_field"]);

if (!$resp->is_valid) {
   die ("The reCAPTCHA was entered incorrectly. Go back and try it again." .
    "(reCAPTCHA said: " . $resp->error . ")");
} else {
   // my code
}

Ultimately, does anyone know why my code is not validating even though I have entered everything correctly according to every tutorial I have found and was able to follow. I have tried entering the < ?php require_once ? > sequence of code as a direct child of the < form > as well as everything else in my form. I have also gone as far as not incorporating the < ?php require_once ? > and end up with the same result.

<form method="post" action="paperclip.php" name="submission" id="contactform" class="form c-form">
    <?php
        require_once('recaptchalib.php');
        $publickey = "6LffWgATAAAAAEfZ6Q0bo57UUz5MwbA3T9dl_uWn";
        echo recaptcha_get_html($publickey);
    ?>
    <fieldset>
        <input name="name" type="text" id="name" placeholder="Your Name" />
        <input name="email" type="text" id="email" placeholder="Your E-Mail" />
        <textarea name="comments" id="comments" placeholder="If you are submitting an entry for the Paperclip Contest, you must include the ad name and page that the paperclip appears."></textarea>
        <div class="six col">
            <div style="float: right;" class="g-recaptcha" data-sitekey="6LffWgATAAAAAEfZ6Q0bo57UUz5MwbA3T9dl_uWn">
            </div>
        </div>
        <div class="six col">
            <div class="text-align: center">
                <input type="submit" class="submit btn color" id="submit" value="Send message" />
            </div>
        </div>
    </fieldset>
</form>

I also have the javascript line:

<script src='https://www.google.com/recaptcha/api.js'></script>

in my < head > of my html file.

Does this sound like an error inside my PHP code after the PHP validation code? If so, please let me know and I can post the remaining of my PHP file.

Any help is greatly appreciate and I will do my best to help with any requests.