Comments on: Zend PHP5 certification Exam study review 11: supplementary II

By: admin

admin — Tue, 07 Oct 2008 13:39:12 +0000

tjmcd1963, I knew what you mean. I think, maybe in the case that you want to test if a class is a singleton? E.g.:

$a = new ForeignClass();
$b = new ForeignClass();
if($a === $b) {echo “It is a singleton.”;} else{echo “It is not a singleton.”;}

Of coures, in the real world, this is a very rare scenario, even you got a class from somewhere, and it was not documented and has no comment, you can always check the source code of the Class right? But I also can’t think another example in the real world right now. But, this is may useful in large project, and you use $a=$b; but after pass $a and $b around, in some places, you forgot you used this stating or it is just another person on the project, so use if($a===$b).
P.S., I think “the same instance of an object” is actually “the same instance of an class”. The question itself seem has a problem.

By: admin

admin — Tue, 07 Oct 2008 13:32:57 +0000

Hi Alexey, you are right. My answers were wrong, it should use unset. Actually, I knew they are wrong a long time ago; I forgot to correct it. And, later, I thought, maybe just keep it as is. I never said that all these here are the “correct answers” :). Thank you very much for your this comments!

By: Alexey

Alexey — Tue, 07 Oct 2008 08:18:52 +0000

Hi!
On question
“To destroy one variable within a PHP session you should use which method in PHP 5?”
you answered
session_destroy(); session_regenerate_id();
Why? To destroy ONE variable you should use unset() method, like unset ($_SESSION['var'])
P.S. Thank you for interesting article

By: tjmcd1963

tjmcd1963 — Mon, 06 Oct 2008 15:17:54 +0000

Here, $a and $b are not the same instance of an object, they are two different instance of the same class, eventhough the if statement will return true…

Ok, I see your point there, but without simply stating that $a=$b; can you provide a simple example wherein $a and $b would in fact be “the same instance of an object” never mind where $a and $b “contain” the same instance? I confess that I am having some difficulty imagining such a scenario in the real world.

By: admin

admin — Sun, 05 Oct 2008 06:30:16 +0000

Yeah, from the manual, it says instanceof can also used with another object or a string variable. However, look at the example#5 on php.net, the use of another object example is:
$a = new MyClass;
$b =new MyClass;
if($a instanceof $b)…

Here, $a and $b are not the same instance of an object, they are two different instance of the same class, eventhough the if statement will return true.

By: tjmcd1963

tjmcd1963 — Sat, 04 Oct 2008 16:24:59 +0000

When checking to see if two variables contain the same instance of an object, which of the following comparisons should be used?
if($obj1 === $obj2) // ??? are you sure it’s not…
if($obj1 instanceof $obj2) // ???
e.g. (from the manual)…
“Although instanceof is usually used with a literal classname, it can also be used with another object or a string variable:”

if($a instanceof $b) echo “foo”;
if($a === $b) echo “bar”;
//returns foo