$db_host = 'localhost';
$db_user = 'user_name';
$db_pass = 'password';
$db_database = 'database_name';
$con = mysql_connect($db_host, $db_user, $db_pass) or die('Unable to establish a DB connection');
$result = mysql_query("DROP TABLE IF EXISTS table_a;", $con);
if ( ! $result ) die("Line: " . __LINE__ . " Error: ". mysql_error());