PHPMailer - gmail smtp not working properly

I have shared two different mail methods for your requirement..

First case;

// Pear Mail Library
require_once "Mail.php";

$from = '<from.gmail.com>';
$to = '<to.yahoo.com>';
$subject = 'Hi!';
$body = "Hi,nnHow are you?";

$headers = array(
    'From' => $from,
    'To' => $to,
    'Subject' => $subject
);

$smtp = Mail::factory('smtp', array(
        'host' => 'ssl://smtp.gmail.com',
        'port' => '465',
        'auth' => true,
        'username' => 'johndoe@gmail.com',
        'password' => 'passwordxxx'
    ));

$mail = $smtp->send($to, $headers, $body);

if (PEAR::isError($mail)) {
    echo('<p>' . $mail->getMessage() . '</p>');
} else {
    echo('<p>Message successfully sent!</p>');
}

Second case; (http://ctrlq.org/code/19589-send-mail-php)

$mail = new PHPMailer;

$mail->isSMTP();                                      // Set mailer to use SMTP
$mail->Host = 'smtp.gmail.com';                       // Specify main and backup server
$mail->SMTPAuth = true;                               // Enable SMTP authentication
$mail->Username = 'amit@gmail.com';                   // SMTP username
$mail->Password = 'digitalinspiration';               // SMTP password
$mail->SMTPSecure = 'tls';                            // Enable encryption, 'ssl' also accepted
$mail->Port = 587;                                    //Set the SMTP port number - 587 for authenticated TLS
$mail->setFrom('amit@gmail.com', 'Amit Agarwal');     //Set who the message is to be sent from
$mail->addReplyTo('labnol@gmail.com', 'First Last');  //Set an alternative reply-to address
$mail->addAddress('josh@example.net', 'Josh Adams');  // Add a recipient
$mail->addAddress('ellen@example.com');               // Name is optional
$mail->addCC('cc@example.com');
$mail->addBCC('bcc@example.com');
$mail->WordWrap = 50;                                 // Set word wrap to 50 characters
$mail->addAttachment('/usr/labnol/file.doc');         // Add attachments
$mail->addAttachment('/images/image.jpg', 'new.jpg'); // Optional name
$mail->isHTML(true);                                  // Set email format to HTML

$mail->Subject = 'Here is the subject';
$mail->Body    = 'This is the HTML message body <b>in bold!</b>';
$mail->AltBody = 'This is the body in plain text for non-HTML mail clients';

//Read an HTML message body from an external file, convert referenced images to embedded,
//convert HTML into a basic plain-text alternative body
$mail->msgHTML(file_get_contents('contents.html'), dirname(__FILE__));

if(!$mail->send()) {
   echo 'Message could not be sent.';
   echo 'Mailer Error: ' . $mail->ErrorInfo;
   exit;
}

echo 'Message has been sent';

Try it and hope it will solve your issues !

You edited your question several times, each time changing its meaning, that should be avoided in future as it generates tones of comments. Instead next time pls, read error messages and fix them before asking. What you did wrong (in order of appearance)

1. Don't use assigning methods without values just for future like $mail->addAddress('');, $mail->addCC(''), etc, it will cause errors.
2. Use proper SMTP server address.
3. Use proper credentials. Of course login and password are case sensitive.
4. Turn ON 'Less secure applications' on your Gmail account if still have problem with credentials errors. It can be done at the security tab as shown at screenshot