[PHP] Re: self:: vs this
Mariano Guadagnini wrote:
Hy people,
I have an existential doubt regarding php classes. I have been a php
programmer for quite a long time, but never could figure out the clear
difference between using this-> or self:: when calling member functions,
wether they are private or public. I used them indistinctly and seemed
to sort the same effects, although, when working with statics classes,
self:: was the only way to access members.
Well, that's all, any can put me some light on the matter?
Thanks,
The clear difference between these two is the way you are calling (and
thus WHAT you are calling aswell).
In PHP you can use classes in 2 ways:
1. statically, you have a class defined as a collection of methods
without actual changable properties.
2. as an instance. You have a class "template" which you instantiate,
thus making what is known commonly as an object.
In case 1, we would have such code as follows:
class Foo {
static function Bar() {
echo 'I am method Bar of Class Foo';
}
}
Foo::Bar();
>> I am method Bar of Class Foo
in case 2:
class Foo {
public function Bar() {
echo 'I am method Bar of an object derived from class Foo';
}
}
$foo = new Foo;
$foo->Bar();
>> I am method Bar of an object derived from class Foo
No real difference there, right?
So, now let's imagine we want to have an object as a collection of both
methods AND properties:
if we were to use the static approach, we now have a problem:
1. you can't store and manipulate static properties (AFAIK)
2. you only have 1 class, changing it here will propagate the change
troughout your entire codebase (for this run)
If we used objects, we wouldn't have to worry about it:
Class Foo {
public $a = 1;
public function Bar() {
$this->a++;
}
}
$foo = new Foo;
echo $foo->a;
>> 1
$foo->Bar();
echo $foo->a;
>> 2
$bar = new Foo;
echo $bar->a; // (new object)!
>> 1
statically:
Class Foo {
static $a = 1;
static function Bar() {
self::a++;
}
}
echo Foo:a;
>> 1
Foo::Bar(); // will probably throw a warning, not sure of that though
echo Foo:a;
>> 1 (no change)
now, if we would want 2 different collections, each with their own value
of Foo:a, we would not be able to use the static way.
Basically what you can remember here is:
:: calls a property or method in a STATIC context (ie. without access to
the object's (if any) actual properties)
-> calls a propert or method in a DYNAMIC context (ie. WITH access to
that specific object's collection of methods and properties).
long talk, but I hope you understand the difference now.
- tul
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[PHP] Re: self:: vs this
self:: static functions $this-> non static functions -- itoctopus - http://www.itoctopus.com "Mariano Guadagnini" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > Hy people, > I have an existential doubt regarding php classes. I have been a php > programmer for quite a long time, but never could figure out the clear > difference between using this-> or self:: when calling member functions, > wether they are private or public. I used them indistinctly and seemed > to sort the same effects, although, when working with statics classes, > self:: was the only way to access members. > > Well, that's all, any can put me some light on the matter? > > Thanks, > > -- > > Mariano Guadagnini > UVCMS S.R.L > www.uvcms.com > > > > -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Re: self:: vs this
On 5/11/07, M.Sokolewicz <[EMAIL PROTECTED]> wrote:
statically:
Class Foo {
static $a = 1;
static function Bar() {
self::a++;
}
}
echo Foo:a;
>> 1
Foo::Bar(); // will probably throw a warning, not sure of that though
echo Foo:a;
>> 1 (no change)
I'm not sure I understand what you mean by this. This code works:
Class Foo {
static $a = 1;
static function Bar() {
self::$a++;
var_dump(self::$a);
}
static function Meh() {
self::$a='asdf';
var_dump(self::$a);
}
}
Foo::Bar();
Foo::Bar();
Foo::Bar();
Foo::Meh();
- output
int 2
int 3
int 4
string 'asdf' (length=4)
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Re: [PHP] Re: self:: vs this
M.Sokolewicz wrote: Basically what you can remember here is: :: calls a property or method in a STATIC context (ie. without access to the object's (if any) actual properties) -> calls a propert or method in a DYNAMIC context (ie. WITH access to that specific object's collection of methods and properties). While that's generally true, self::, parent::, ClassName:: and ParentClassName:: can all be used in both contexts when calling methods. Consider the following code: At first glance these all appear to be static method calls, but $this is available in every case. Arpad -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Re: self:: vs this
On Fri, May 11, 2007 12:28 pm, Eric Butera wrote:
> On 5/11/07, M.Sokolewicz <[EMAIL PROTECTED]> wrote:
>> statically:
>> Class Foo {
>> static $a = 1;
>> static function Bar() {
>>self::a++;
>> }
>> }
Use self:: only when you don't have an actual instance handy, is a
general rule, I think...
self:: is kinda like using the Plato-like "ideal" of the class --
there's no actual instantiated real-world "thing" to work on.
You're working with an abstract non-existant idealized non-object.
$x (or $this) you are working with an actual real-life instantiated
"object".
Disclaimer:
This is how I thought of it in C++, rather than a ton of experience in
PHP...
PS
PHP 6 may become more "strict" about using / not using self:: where it
"should" be used... Depends on how the Internals 'discussions' pan
out...
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