Basic php form using recatcha v2 and curl

index.html

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

<div id="contact_form">
			<h1>Contact Form</h1>
				<form method="POST" action="includes/php/mail.php">
				
					<p class="">
					Your Name:</p>
					<input class="" name="name" type="text" size="25" maxlength="100" />
					<br /><br />
				
					<p class="">
					Your Email Address:</p>
					<input class="" name="email" type="text" size="25" maxlength="100" />
					<br /><br />
					
					<p class="">
					Your Phone Number:</p>
					<input class="" name="telephone" type="text" size="25" maxlength="100" />
					<br />
					<br />
					<p class="">
					Your Message:
					</p><textarea class="" name="message"></textarea>
					<br />
					<div class="g-recaptcha" data-sitekey="6Lfon34UAAAAAGS_cI1a21CEFd4xCkBytB4VvMpt"></div>
					<br />
					<div id="submit">
						<p><input type="submit" value="Send Email" name="submit" />
						<input type="reset" value="Clear Form" /></p>
					</div>
				</form>
			</div>

mail.php

<?php

if(isset($_POST['submit']) && !empty($_POST['submit'])):
    if(isset($_POST['g-recaptcha-response']) && !empty($_POST['g-recaptcha-response'])):

        //your site secret key
        $secret = '!!!SECRET_KEY_GOES_HERE!!!!';
        $ip = $_SERVER['REMOTE_ADDR'];

        // create a new cURL resource
        $ch = curl_init();

        // set URL and other appropriate options
        curl_setopt($ch, CURLOPT_URL, 'https://www.google.com/recaptcha/api/siteverify?secret='.$secret.'&response='.$_POST['g-recaptcha-response'].'&remoteip='.$ip);

        //Prevent printing curl object on page, instead store data in response variable below and decode json
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);

        // grab URL and pass it to the browser
        $response = curl_exec($ch);
        $responseData = json_decode($response);

        // close cURL resource, and free up system resources
        curl_close($ch);
  
        if($responseData->success):
            //contact form submission code
            $name = !empty($_POST['name'])?$_POST['name']:'';
            $email = !empty($_POST['email'])?$_POST['email']:'';
            $telephone = !empty($_POST['telephone'])?$_POST['telephone']:'';
            $message = !empty($_POST['message'])?$_POST['message']:'';
            
            $to = '[email protected]';
            $subject =  $_POST['subject'];
            $body = "
                <h1>Contact request details</h1>
                <p><b>Name: </b>".$name."</p>
                <p><b>Email: </b>".$email."</p>
                <p><b>Telephone: </b>".$telephone."</p>
                <p><b>Message: </b>".$message."</p>";


            // Always set content-type when sending HTML email
            $headers = "MIME-Version: 1.0" . "\r\n";
            $headers .= "Content-type:text/html;charset=UTF-8" . "\r\n";
            // // More headers
            $headers .= 'From:'.$name.' <'.$email.'>' . "\r\n";
            
            //send email
            mail($to,$subject,$body,$headers);
            
            //Successful form submission - message then redirect to thank you page for tracking in GA
            echo '<h1>Success!</h1><p>Your contact request has submitted successfully.</p>';
            echo '<script>setTimeout(function(){window.location = "https://mywebsite.com/thank-you-page"}, 3000)</script>';
        else:
            $errMsg = '<h1>Error</h1><p>Robot verification failed, please try again.</p>';
            echo $errMsg;

        endif;
    else:
        $errMsg = '<h1>Error</h1><p>Please click on the reCAPTCHA box.</p>';
        echo $errMsg;
    endif;
else:
    $errMsg = '';
    $succMsg = '';
endif;


?>