Почему Ajax постоянно выдает ошибку?

$(document).ready(function() { 
 
    //E-mail Ajax Send 
    $(".form-present").submit(function() { //Change 
        var th = $(this); 
        $.ajax({ 
            type: "POST", 
            url: "mail.php", //Change 
            data: th.serialize() 
        }).done(function() { 
            alert("Thank you!"); 
            setTimeout(function() { 
                // Done Functions 
                th.trigger("reset"); 
            }, 1000); 
        }); 
        alert("Ошибка"); 
        return false; 
    }); 
 
});

<form class="form-present"> 
 
                    <!-- Hidden Required Fields --> 
                    <input type="hidden" name="project_name" value="Site Name"> 
                    <input type="hidden" name="admin_email" value="blabla@gmail.com"> 
                    <input type="hidden" name="form_subject" value="Form Subject"> 
                    <!-- END Hidden Required Fields --> 
 
                    <input class="input" value="" type="text" required name="name_present" placeholder="Введите имя"> 
                    <input class="input"  value="" type="tel" required name="tel_present" placeholder="Введите телефон"> 
                <button class="button_form button-present" type="submit">Получить подарок</button> 
                </form>

<?php 
 
$method = $_SERVER['REQUEST_METHOD']; 
 
//Script Foreach 
$c = true; 
if ( $method === 'POST' ) { 
 
	$project_name = trim($_POST["project_name"]); 
	$admin_email  = trim($_POST["admin_email"]); 
	$form_subject = trim($_POST["form_subject"]); 
 
	foreach ( $_POST as $key => $value ) { 
		if ( $value != "" && $key != "project_name" && $key != "admin_email" && $key != "form_subject" ) { 
			$message .= " 
			" . ( ($c = !$c) ? '<tr>':'<tr style="background-color: #f8f8f8;">' ) . " 
				<td style='padding: 10px; border: #e9e9e9 1px solid;'><b>$key</b></td> 
				<td style='padding: 10px; border: #e9e9e9 1px solid;'>$value</td> 
			</tr> 
			"; 
		} 
	} 
} else if ( $method === 'GET' ) { 
 
	$project_name = trim($_GET["project_name"]); 
	$admin_email  = trim($_GET["admin_email"]); 
	$form_subject = trim($_GET["form_subject"]); 
 
	foreach ( $_GET as $key => $value ) { 
		if ( $value != "" && $key != "project_name" && $key != "admin_email" && $key != "form_subject" ) { 
			$message .= " 
			" . ( ($c = !$c) ? '<tr>':'<tr style="background-color: #f8f8f8;">' ) . " 
				<td style='padding: 10px; border: #e9e9e9 1px solid;'><b>$key</b></td> 
				<td style='padding: 10px; border: #e9e9e9 1px solid;'>$value</td> 
			</tr> 
			"; 
		} 
	} 
} 
 
$message = "<table style='width: 100%;'>$message</table>"; 
 
function adopt($text) { 
	return '=?UTF-8?B?'.Base64_encode($text).'?='; 
} 
 
$headers = "MIME-Version: 1.0" . PHP_EOL . 
"Content-Type: text/html; charset=utf-8" . PHP_EOL . 
'From: '.adopt($project_name).' <'.$admin_email.'>' . PHP_EOL . 
'Reply-To: '.$admin_email.'' . PHP_EOL; 
 
mail($admin_email, adopt($form_subject), $message, $headers );