Mailchimp API HTML

<div style="background: rgba(0,0,0,0.4); border: 2px solid #fff; padding: 20px 15px; margin: 50px 0; border-radius: 5px; "> 
<h3 style="color: #fff; text-align: center; margin-bottom: 10px;"> Newsletter </h3>

<script>
jQuery(document).ready(function($) {
$("#subscribe2").click(function(){
	var pattern = new RegExp(/^(("[\w-\s]+")|([\w-]+(?:\.[\w-]+)*)|("[\w-\s]+")([\w-]+(?:\.[\w-]+)*))(@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$)|(@\[?((25[0-5]\.|2[0-4][0-9]\.|1[0-9]{2}\.|[0-9]{1,2}\.))((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\.){2}(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\]?$)/i);

  var name=$('#name2').val();
  var email=$('#email2').val();
  var listId=''; //list ID

if(pattern.test(email) && name)
{
  $.ajax({url:"http://www.submit_url.com/wp-admin/admin-ajax.php",type:"post",data:"action=send_newsletter&name="+name+"&email="+email+"&listId="+listId,success:function(result){
	result = result.replace("0", ""); 
	if(result=='ok')
{
result='Thank you for subscribing to our newsletter.';	
$('#result2').css('color','#fff');
}
	else
	{
		result=email+' is already subscribed to our newsletter list.';
		$('#result2').css('color','red');
	}
	$('#result2').html(result);

  }});
}
});

});
</script>

<p id="result2" style="text-align:center"></p>
<form id="newsletter" action="javascript:void(0)">
<input type="text" name="newsletter_name" id="name2" class="newsletter_name" placeholder="Your Name" required="required" />
<input type="email" name="newsletter_email" id="email2" class="newsletter_email" placeholder="Your Email" required="required" />
<input type="submit" class="newsletter btn" id="subscribe2" value="SUBSCRIBE" />
</form>

</div>

WordPress function.php file

/* Mail Chimp API */

add_action( 'wp_ajax_nopriv_send_newsletter', 'send_newsletter' );
add_action( 'wp_ajax_send_newsletter', 'send_newsletter' );	
	

	function send_newsletter()
	{
		$email=$_POST['email'];		
		$name=$_POST['name'];	

		if($name && $email)
		{
			
			$submit_url = "https://us11.api.mailchimp.com/2.0/lists/subscribe.json"; //Submit URL
						
			$send_data=array(
				'email'=>array('email'=> $email),
				'apikey'=>"", //API key 
				'id'=>"a482308945",
				'merge_vars'=> array('FNAME'=>$name),
				'double_optin'=>false,
				'update_existing'=>false,
				'replace_interests'=>false,
				'send_welcome'=>false,
				'email_type'=>"html",
			);
			$payload = json_encode($send_data);
			 
			$ch=curl_init();
			curl_setopt($ch,CURLOPT_URL,$submit_url);
			curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
			curl_setopt($ch,CURLOPT_POST,true);
			curl_setopt($ch,CURLOPT_POSTFIELDS,$payload);
			$result=curl_exec($ch);
			curl_close($ch);

			$data = json_decode($result);
			if (isset($data->error)){
				echo $data->error;
			} else {
				echo "ok";
			}
		}
		else
		echo 'Error!!!!';

	}