Using isset() empty() and is_null()
Validating the input is very important, but you want te write lean code. So if you are in doubt
about using !empty only, or !empty && isset here’s the difference:
| Value of variable ($var) | isset($var) | empty($var) | is_null($var) |
|---|---|---|---|
| “” (an empty string) | bool(true) | bool(true) | bool(false) |
| ” ” (space) | bool(true) | bool(false) | bool(false) |
| FALSE | bool(true) | bool(true) | bool(false) |
| TRUE | bool(true) | bool(false) | bool(false) |
| array() (an empty array) | bool(true) | bool(true) | bool(false) |
| NULL | bool(false) | bool(true) | bool(true) |
| “0” (0 as a string) | bool(true) | bool(true) | bool(false) |
| 0 (0 as an integer) | bool(true) | bool(true) | bool(false) |
| 0.0 (0 as a float) | bool(true) | bool(true) | bool(false) |
| var $var; (a variable declared, but without a value) | bool(false) | bool(true) | bool(true) |
| NULL byte (“\ 0”) | bool(true) | bool(false) | bool(false) |