Clear analysis of phpunset () and null variables

Unset (mixedvar [, mixedvar [,]) unset () destroys the specified variable. Note that in php3, unset () returns true (actually an integer value ).

Unset (mixed var [, mixed var [,...])

Unset () destroys the specified variable. Note that in php 3, unset () will return true (actually an integer value of 1). in php 4, unset () is no longer a real function: it is now a statement, so that no return value is returned. an attempt to obtain the return value of unset () will cause a parsing error.

Null bytes indicate that the variable is null $ t = ''. the variable has a value, but is null. the isset () parameter is true.

The null constant is $ t = null. the variable has no value, and is not empty. the isset () is false.

2. $ A = array (
3. 'A' => 'A ',
4. 'B' => 'B'
5. );
6. $ B = array (
7. 'A' => 'A ',
8. 'B' => 'B'
9. );
10. $ A ['B'] = null;
11. Unset ($ B ['B']);
12. Print ('

    ');  

13. Print_r ($ );
14. Print (' ');
15. Print_r ($ B );
16. Print ('');
17. ?>
18. /* Result:
19. Array
20. (
21. [A] =>
22. [B] =>
23. )
24. Array
25. (
26. [A] =>
27. )*/