how it works? pass a function as array(&$sess_handler, 'open') instead of '$sess_handler->open'

**Janwillem Borleffs** · Apr 17 '06, 11:45 AM

Re: how it works? pass a function as array(&$ses s_handler, 'open') instead of '$sess_handler->open'

_Mario.lat wrote:[color=blue]
> How does it works?
> why it use "array(&$sess_h andler, 'open')" and not
> "$sess_hand ler->open" ? How "array(&$sess_h andler, 'open')" works?
>[/color]

You should read this as array(reference _to_object, object_method_t o_call);

In this case, when the session starts, the 'open' method within the
$sess_handler object instance is called with $savePath and $sessName as its
arguments. Where $sess_handler->open is a property call, the passing of the
array containing the object instance and the method (handler) name, only
sets up the specific session handler for later usage.

BTW, there are other functions using the same scheme, like call_user_func:

class Foo {
function Bar($name) {
print "Hello $name";
}
}

call_user_func( array(new Foo, 'Bar'), 'John');

HTH;
JW

**Jerry Stuckle** · Apr 17 '06, 11:55 AM

Re: how it works? pass a function as array(&$ses s_handler, 'open')instead of '$sess_handler->open'

_Mario.lat wrote:[color=blue]
> Hallo,
> I have a little question:
> In the function session_set_sav e_handler I can pass the name of function
> which deal with session.
> In Xoops code I see the use of this function like that:
>
> session_set_sav e_handler(array (&$sess_handler , 'open'),
> array(&$sess_ha ndler, 'close'), array(&$sess_ha ndler, 'read'),
> array(&$sess_ha ndler, 'write'), array(&$sess_ha ndler, 'destroy'),
> array(&$sess_ha ndler, 'gc'));
>
> How does it works?
> why it use "array(&$sess_h andler, 'open')" and not "$sess_hand ler->open"
> ? How "array(&$sess_h andler, 'open')" works?
> Thank you in advance for the time you'll spend for me. Mario.
>
>[/color]

<code snipped>

You can't just pass $sess)handler->open to the function because it is a member
(method) of a class. And to call a non-static method, you need an object of
that class.

$sess_handler->open is just a pointer to the function; it doesn't have an object
associated to it. So if you were to call it, there would be no object for the
method to use.

OTOH, when you pass array(&$sess_ha ndler, 'open'), you are passing an object
($sess_handler) by reference. You are also passing the name of a method
('open') as a string. So session_set_sav e_handler has all it needs to use the
class - an object and a method. And it has this information for each of the six
methods it needs.

Hope this is clear.

--
=============== ===
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attgl obal.net
=============== ===

**Sjoerd** · Apr 17 '06, 11:55 AM

Re: how it works? pass a function as array(&$ses s_handler, 'open') instead of '$sess_handler->open'

> session_set_sav e_handler(array (&$sess_handler , 'open'),

The first parameter would be the object on which to invoke a method.
The second parameter would be the name of the method ('open').

In session_set_sav e_handler, when an open occurs, it calls
$sess_handler->$name_of_metho d. The method $sess_handler->open is
actually a callback function.

Without the use of objects, a callback function would be a normal
function. You would pass the name of the function as a parameter:

<?php
function foo($functionna me) {
echo $functionname(' hello');
}

foo('strtoupper ');
?>

As you can see, 'strtoupper' is passed as a parameter and then used as
a function.

This won't work for objects:
<?php
foo('$obj->open');
foo('Object::Op en');
?>

The first does not work because the variable $obj is not passed
correctly. The second way also does not work, but I can not think of a
good reason why it doesn't.

The right way, design-wise, to set a handler is to pass an object which
implements an interface. The interface specifies which methods an
object has to have, such as open, close, etc. You then pass an object
which implements this interface and the methods within this object can
be called.

d · Apr 17 '06, 08:15 PM

Re: how it works? pass a function as array(&$ses s_handler, 'open') instead of '$sess_handler->open'

"Sjoerd" <sjoerder@gmail .com> wrote in message
news:1145274125 .993793.71410@g 10g2000cwb.goog legroups.com...[color=blue][color=green]
>> session_set_sav e_handler(array (&$sess_handler , 'open'),[/color]
>
> The first parameter would be the object on which to invoke a method.
> The second parameter would be the name of the method ('open').
>
> In session_set_sav e_handler, when an open occurs, it calls
> $sess_handler->$name_of_metho d. The method $sess_handler->open is
> actually a callback function.
>
> Without the use of objects, a callback function would be a normal
> function. You would pass the name of the function as a parameter:
>
> <?php
> function foo($functionna me) {
> echo $functionname(' hello');
> }
>
> foo('strtoupper ');
> ?>
>
> As you can see, 'strtoupper' is passed as a parameter and then used as
> a function.
>
> This won't work for objects:
> <?php
> foo('$obj->open');
> foo('Object::Op en');
> ?>
>
> The first does not work because the variable $obj is not passed
> correctly. The second way also does not work, but I can not think of a
> good reason why it doesn't.[/color]

It's because of the :: - that's part of the language, and not a part of the
variable name. $object::$func would be the equivalent, but that requires
two parameters to pass, whereas using an array means it's one parameter,
which means it's the same for functions and member functions.
[color=blue]
> The right way, design-wise, to set a handler is to pass an object which
> implements an interface. The interface specifies which methods an
> object has to have, such as open, close, etc. You then pass an object
> which implements this interface and the methods within this object can
> be called.
>[/color]

how it works? pass a function as array(&$sess_handler, 'open') instead of '$sess_handler->open'

how it works? pass a function as array(&$sess_handler, 'open') instead of '$sess_handler->open'

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