Dump wp database by file

mysqldump.php

<?php

if ( ! defined( 'ABSPATH' ) ) {
	define( 'ABSPATH', dirname( __FILE__ ) . '/' );
}

error_reporting( E_CORE_ERROR | E_CORE_WARNING | E_COMPILE_ERROR | E_ERROR | E_WARNING | E_PARSE | E_USER_ERROR | E_USER_WARNING | E_RECOVERABLE_ERROR );

if ( file_exists( ABSPATH . 'wp-config.php') ) {

	require_once( ABSPATH . 'wp-config.php' );

}

header( 'Content-Type: application/x-gzip' );
header( 'Content-Disposition: attachment; filename="mysqldump.sql.gz"' );

$cmd = 'mysqldump -u %s -h %s --password=%s %s | gzip --best';
$cmd = sprintf( $cmd, DB_USER, DB_HOST, DB_PASSWORD, DB_NAME ); 

passthru( $cmd );

exit(0);