End my $this pain

[SeanColeman]

This may have been answered already, but try searching for $this. 

Anyhoo, I would love to find out definitively, without any doubt, what the heck it means?

How is it used? (If you leave a code example, please use anything but FOO!!  )

And, what is $this->output.= '</table>'; doiing? (Just an example)

I know that it is somehow performing "echo" or "print" but what is -> doing and where is all this (pardon the pun) coming from?

 

I'm a self taught PHP muddler, so the whole function/method thing is a vague concept to me. I get the jist, but not anywhere near a commanding understanding. I'm looking for the dumb-down explanation.

 

 

 

[Balmung-San]

This (no pun intended) is based on Object Oriented standards. When you've written a class $this will literally mean this instance of this object. Example:

 

<?php
class A{
public $var1 = "";

public function speak(){
echo $this->var1;
}
}

$a = new A();
$a->var1 = "hello\n";
$a->speak();

$b = new A();
$b->var1 = "world\n";
$b->speak();
$a->speak();
?>

 

This will output:

hello
world
hello

[wildteen88]

the variable $this is used to access objects (variables) and methods (functions) within a class.

[SeanColeman]

Wow. That means I'm about to get a bigger headache.

I am playing with a 200 line page and it's all for a class with about way-too-many $thises (yep, that's a new word) in it. So each time I see $this, it is refering to any variable/functions within the class it's under?

 

I feel my eyes bugging as I write.  :'(

[Balmung-San]

Yup. That's exactly how it works. Just remember it's that instance of that object. Unless the variable is a constant (and static? do PHP statics work like Java statics?), it will probably be different for each instance of the class.

[SeanColeman]

Alrighty, so here's bit of the first few lines. It's a calendar thingy. First line of the included Class is protected $ID; So, that means $this->ID = $ID."_"; in the below is refering to $ID from the included file controls.php (Plus the underscore)?

 

include_once("controls.php");

 

class Calendar extends Controls

{

.........

 

public function Calendar($ID, $Date = NULL)

{

$this->ID = $ID."_";

...

                ...

[KrisNz]

Yup, whats its doing is setting the 'protected $ID' - a property of the calendar to the value contained in $ID - the first argument of the function. That particular function is what's known as a constructor, and its called automatically when you create an instance of the object.

E.g

$cal = new Calendar(1,'2007-01-11'); //I dont know how it expects the date to be formatted so that may not work, its just an example
echo $cal->ID; //echos '1_' because the constructor has been called and the objects property has been set to 1 and concatenated with an underscore by the constructor

Because that property is marked as protected, it means that its value can only be changed by that class or any class that extends it. So if you tried to go

$cal->ID = "some crazy value";

You would get an error.

[SeanColeman]

Thank you very much! My confusion was coming from the "extension" of the included file, had no idea that $this reached that document. This should definitely make it easier to pick it apart, but I'm sure I'll be back. I have to now figure out where the thing is hiding the resulting $_POST.

 

Onward!

And thanks again everyone.