Backing up databases

<?php

date_default_timezone_set('Asia/Calcutta');
require_once "../../variables.php";
$gmessage = "Backing up databases\r\n\r\n";

function backup($sitename, $db_user, $db_pass)
	{
		$db_server	= $db_user.'.db.3740856.hostedresource.com';	// Database server, usually "localhost"
		$db_name	= $db_user;		// Database name, leave empty for 'all databases'
		$to			="[email protected], [email protected]"; // Address to wihch mail is to be sent
		$subject = "Backup of ".$sitename." at ".date('Y-m-d-H-i-s'); // subject of mail
		$headers = 	"From: ".$sitename."@dak.me\r\n";

		$bound_text = "Bound Text";
		$bound = 	"--".$bound_text."\r\n";
		$bound_last = 	"--".$bound_text."--\r\n";  // ========= I don't understand these three lines and their purpose ===

			$date_stamp         = date('Y-m-d-H-i-s');
			$backup_filename = ($db_name == '' ? 'all_databases' : $db_name) . '_' . $date_stamp . '.sql.gz';
			$cmd = 'mysqldump -u ' . $db_user . ' -h ' . $db_server . ' --password=' . $db_pass . ' ' . ($db_name == '' ? '--all-databases' : $db_name) . ' | gzip > ' . $backup_filename;
			$dump_status = (passthru($cmd) === false) ? 'No' : 'Yes';

		$headers .= 	"MIME-Version: 1.0\r\n"
			."Content-Type: multipart/mixed; boundary=\"$bound_text\"";

		$message .= 	"If you can see this MIME than your client doesn't accept MIME types!\r\n"
			.$bound;

		$message .= 	"Content-Type: text/html; charset=\"iso-8859-1\"\r\n"
			."Content-Transfer-Encoding: 7bit\r\n\r\n"
			."Thank you for using dak database script from http://dak.me by <A HREF='http://mukeshdak.com'>Mukesh Dak</A>\r\n"
			.$bound;

		$file = file_get_contents("http://zdak.in/dcode/cron/".$backup_filename);   // ======= don't forget to update this path ===========

		$message .= 	"Content-Type: application/x-zip-compressed; name=$backup_filename\"\r\n"
			."Content-Transfer-Encoding: base64\r\n"
			."Content-disposition: attachment; file=$backup_filename\r\n"
			."\r\n"
			.chunk_split(base64_encode($file))
			.$bound_last;

		if($dump_status="Yes")
			{
				if(mail($to, $subject, $message, $headers))
				{
					// $gmessage .= "Backup of database ".$db_name." of ".$sitename." has been sent to ".$to."\r\n";
					 unlink($backup_filename);
				} else {
					 $gmessage .= 'MAIL FAILED';
				}
				}
			else{
					$gmessage .= "<p>There is some problem in taking dump of your database";
				}
		return "Backup of database ".$db_name." of ".$sitename." has been sent to ".$to."\r\n";
	}  // function backup ends here

	ConnectDB();

	$result = mysql_query("SELECT * FROM ".TBL_DAKDATABASE." WHERE prepared='1'") or die("<p>Error in Table Selection: ".mysql_error());

	while($row = mysql_fetch_assoc($result))
					{
						$gmessage .= backup($row['linkurl'], $row['title'], $row['category']);
					}
	mysql_close(); // Close database connection
	//$gmessage .= backup('ShreeCement', 'shreecement', 'spiceS500');
				// backup of this database is causing problem

	$gmessage .= "\r\nDatabase backup job completed ".$_SERVER["PHP_SELF"]."\r\n\r\n";
	$gmessage .= "\r\n Script: http://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI']."\r\n\r\n";

	mail("[email protected]", "Subject: Backupsuccessful", $gmessage, "From: [email protected]" );
	// send backup details to gmail without attachment
	echo "If you dont see any errors, everything went as planned";
?>