PHP rozdiel medzi isset() & is_null()

[Richard Willmann]

> IsSet() Ti rekne jestli vubec promenná existuje a má nejakou hodnotu (byt
> nulovou) a Is_Null() overuje, jestli existující promenná má nastavenou
> hodnotu na nulu.
>     Sorryza tykání,  ale jednako uz mám upito a hlavne mi tykání prijde
méne
> odtazité

no ani moc nie, teda aspon podla manualu...

---

bool is_null ( mixed var)
Returns TRUE if var is null, FALSE otherwise.

---

boolean isset ( mixed var [, mixed var [, ...]])

Note: isset() is a language construct.
Returns TRUE if var exists; FALSE otherwise.
If a variable has been unset with unset(), it will no longer be isset().
isset() will return FALSE if testing a variable that has been set to NULL.
Also note that a NULL byte ("\0") is not equivalent to the PHP NULL
constant.

---

pricom NULL je definovane ako

The special NULL value represents that a variable has no value. NULL is the
only possible value of type NULL.
Note: The null type was introduced in PHP 4


takze priznam sa moc nerozumiem naco dve funkcie, lebo:

$a = NULL
isset($a);  // = 0
!is_null($a); // = 0

// $b neexistuje, nebolo vykonane ziadne priradenie
isset($b);  // = 0
!is_null($b); // = 0

$a = 1
isset($a);  // = 1
!is_null($a); // = 1


???

rwi