http://php.net/manual/en/function.empty.php empty에 해당 하는 요소들. Return Values ¶Returns FALSE if var exists and has a non-empty, non-zero value. Otherwise returns TRUE.The following values are considered to be empty:"" (an empty string)0 (0 as an integer)0.0 (0 as a float)"0" (0 as a string)NULLFALSEarray() (an empty array) example empty() / isset()