phpmailer SMTP错误

I am using this php code to send email through gmail account . but its showing smtp error . I have googled it . but not found any specific answer . would anyone please help to find the solution ??

I have hosted this code in my webserver

error : "SMTP Error: Could not connect to SMTP host. Message was not sent Mailer Error: SMTP Error: Could not connect to SMTP host.SMTP Error: Could not connect to SMTP host."

code:

<?php
require("class.phpmailer.php");

$email = $_POST['email_address'];

$username = 'username@gmail.com';  //your gmail address
$password = 'password';  //password


send_mail_to_subscriber();


function send_mail_to_subscriber()
{

    global $username,$password,$email;
    $mailer = new PHPMailer();
    $mailer->IsSMTP();
    $mailer->Host = 'ssl://smtp.gmail.com:465';
    $mailer->SMTPAuth = TRUE;

    $mailer->Username = $username;  
    $mailer->Password = $password;  
    $mailer->From = $username;  
    $mailer->FromName = $username; 

    $mailer->Body = 'this is a message';
    $mailer->Subject = 'this is a subject';
    $mailer->AddAddress($email);  
    if(!$mailer->Send())
    {
       echo "Message was not sent<br/ >";
       echo "Mailer Error: " . $mailer->ErrorInfo;
    }
    else
    {
       echo "Download link has been sent to your email address";
    }
}


?>

Change your Host and add the following:

$mailer->SMTPSecure = 'ssl';
$mailer->Host = 'smtp.gmail.com';
$mailer->Port = 465;

    $mail->SMTPDebug  = 3;     // Enable verbose debug output
    $mail->Mailer       = "smtp";
    $mail->setCharset   = "UTF-8";
    $mail->isSMTP();
    $mail->SMTPDebug    = 0;      // Set mailer to use SMTP
    $mail->Host         = 'smtp.gmail.com'; //Specify main and backup SMTPservers
    $mail->SMTPAuth     = true;         // Enable SMTP authentication
    $mail->Username     = 'gmail user name';     // SMTP username
    $mail->Password     = 'gmail password';                 // SMTP password
    $mail->SMTPSecure   = 'tls';                            // Enable TLS encryption, `ssl` also accepted
    $mail->Port         = 'Your Outgoing server port number';// TCP port to connect to
    $mail->From         = 'from address ';
    $mail->FromName     = ' from name';

To Identify the Issues, Change the value $mail->SMTPDebug = 1,2.3.4.