gmail-imap.php

<?php

// Turn off all error reporting
error_reporting(0);

// Configuration
$user = 'your_login';
$password = 'you_password';
$host = 'imap.gmail.com';

// Default data array
$items = array(
	'msg' => array(), 
	'unseen_items' => array()
);

// Open an IMAP stream to a mailbox
$mailbox = imap_open("{" . $host . ":993/imap/ssl}INBOX", $user, $password, OP_READONLY);

if ($mailbox === false) {
	echo 'Error : ' . imap_last_error();
} else {
	// Gets status information about the given mailbox
	$status = imap_status($mailbox, "{" . $host . "}INBOX", SA_ALL);
	if ($status === false) {
		echo 'Error : ' . imap_last_error();
	} else {
		$items['msg']['all'] = $status->messages;
		$items['msg']['unseen'] = $status->unseen;

		// No unseen messages
		if ($status->unseen == 0) {
			echo 'No unseen messages';
		} else {
			// Gets UIDs for unseen messages
			$messages = imap_search($mailbox, 'UNSEEN');

			if ($messages === false) {
				echo 'Error : ' . imap_last_error();
			} else {
				// For each all unseen messages
				foreach($messages as $uid ) {
					// Get header of the message
					$message = imap_headerinfo($mailbox, $uid);

					if ($message) {
						// From message
						$from = $message->from[0];
						$from_addres = $from->mailbox . "@" . $from->host;

						// Subject
						$subject = isset($message->subject)
							? imap_utf8($message->subject) : 'No subject';

						// Re-format date
						$date = date("Y-m-d H:i", strtotime($message->date));

						// Add to data array
						$items['msg']['unseen_items'][] = array(
							$uid, $from_addres, $date, $subject
						);
					}
				}
			}
		}
	}

	// Close an IMAP stream
	imap_close($mailbox);
}

// Show messages from data array
echo '<pre>' . print_r($items, true) . '</pre>';

Even with the correct email password, Throws error: Error : Can not authenticate to IMAP server: [ALERT] Please log in via your web browser: https://support.google.com/mail/
And at the same moment got email from Gmail, that you some less secure app tried to access your account.
It seems one must change settings in Gmail to allow less secure app and then IMAP will work.

You should use App Passwords in order to access the emails https://support.google.com/accounts/answer/185833

@miljushm Thanks. This gist was created 7 years ago. Only for my tests and fun. I don't want to change anything.

You don't need to change anything because it works well, I just left the comment for the future in case somebody like @motsmanish has the issue with the login to Gmail (it now requires App Passwords) ;)