警告:trim(）要求参数1为字符串，在第973行的wp-includs/class-phpmailer.php中给出的

我正试图使用函数wp_mail从wordpress网站发送电子邮件，但我收到了以下错误：

Warning: trim() expects parameter 1 to be string, array given in /var/www/html/wp-includes/class-phpmailer.php on line 973 0

我真的不明白我为什么会得到它。

这是我当前的代码：

// Contact form  Ajax 
add_action('wp_ajax_nopriv_submit_contact_form', 'submit_contact_form'); 
function submit_contact_form(){
    if(isset($_POST['email'])) {
        $email = $_POST['email'];       
        $email_to = "info@yyy.com";
        $host = "ssl://smtp.gmail.com:465";
        $username = 'myEmail@gmail.uk';
        $password = 'mypassword';
        $email_subject = "You have a new email from $email via yyy.com website";
        $message = $_POST['text']; 
        $headers = array ('From' => $email, 'To' => $email_to,'Subject' => $email_subject);
        /*$smtp = Mail::factory('smtp',
          array ('host' => $host,
            'auth' => true,
            'username' => $username,
            'password' => $password));*/
        //$mail = $smtp->send($email_to, $headers, $message);
        wp_mail( $email_to, $headers, $message );
        /*if (PEAR::isError($mail)) {
          echo($mail->getMessage());
        } else {
          echo("Message successfully sent!'n");
        }*/
    }
}

error_reporting(E_ALL);
ini_set("display_errors", 1);