Mail is not sending in php

Question

My code to send mail from PHP:

 public function send_credentials($beneficiary_user){

  $this->load->library(‘email’);
  $email_config = Array(
        'protocol'  => 'smtp',
        'smtp_host' => 'ssl://smtp.googlemail.com',
        'smtp_port' => '465',
        'smtp_user' => 'app123testing@gmail.com',
        'smtp_pass' => 'apptesting',
        'mailtype'  => 'html',
        'starttls'  => true,
        'newline'   => "\r\n"
    );
    $this->email->from('app123testing@gmail.com', 'invoice');
    $this->email->to('anilapu@navaratan.com');
    $this->email->subject('Invoice');
    $this->email->message('Test');

    $this->email->send();

}

What are the other settings I have to do to make it work *After running echo $this->email->print_debugger();. I got:

Unable to send email using PHP mail(). Your server might not be configured to send mail using this method.

User-Agent: CodeIgniter
     Date: Sun, 9 Feb 2014 14:58:44 +0530
     From: "invoice" 
     Return-Path: 
     Reply-To: "app123testing@gmail.com" 
     X-Sender: app123testing@gmail.com
     X-Mailer: CodeIgniter
     X-Priority: 3 (Normal)
     Message-ID: <52f74a4c41e32@gmail.com>
     Mime-Version: 1.0
     Content-Type: multipart/alternative; boundary="B_ALT_52f74a4c41e88"
      =?utf-8?Q?Invoice?=
      This is a multi-part message in MIME format.
      Your email application may not support this format.
     --B_ALT_52f74a4c41e88
     Content-Type: text/plain; charset=utf-8
     Content-Transfer-Encoding: 8bit
     Test
     --B_ALT_52f74a4c41e88
     Content-Type: text/html; charset=utf-8
     Content-Transfer-Encoding: quoted-printable
    Test
    --B_ALT_52f74a4c41e88--