Classes: Using @, &, :: what does it all mean?

buildernaut1

I'm trying to get into OOP with some of my apps and am having a hard time finding resources on different methods of accessing classes and so on. I've seen various ways to start a class and access it, but don't understand the difference. Anyone have some insight?

I currently use $a = new class();
but have seen:

$a = &new class()
with the '&'

and $a = new class
without the () 'guessing no vars in this classes contructor?'

and $a = new class, $a::class_function()
'looks like C++ syntax ' why :: instead of ->'?

and I can't remember where I saw @ being used, but curious about it as well.

Thanks

laserlight

Read the PHP Manual on classes.

As for @, it is the error suppression operator.

trooper

OK here is an asnwer to help you out

$a::class_function() means make a call to the method "class_function" that exsits in the class that the variable "$a" type of - (did i say that right?)

By doing this you are then removing the requirement to instantiate the class (that is say "$a = new classname").

There are pros and cons about doing it this way ..... i'll leave you to find them out.

Happy reading

ahundiak

http://www.php.net/manual/en/language.oop.php
Look about half way down in the user comments for a post dated 09 Dec 2002. It explains why it's usually a good idea to

$object =& new Class();

Basically, without the & operator, $object actually receives a copy of the object which is a bit wasteful and could (in rare cases) cause problems.

By the way, most of this reference stuff is supposed to go away in PHP 5.

128kb_com

As ahundiak just pointed out, using the & operator when instanciating classes will return a reference to the class as opposed to returning a complete copy.

The & opertor doesn't actually have to be written as $a =& new Foo();, it can be just as well written as $a = &new Foo();. The same goes for variables $a = &$b;. To be clear the = and & are two separate operators that can be used conjunctively.

When using the & with in a function declaration, you can force function parameters to be passed by reference:

 function foo(&$bar) {
   $bar += 10;
}

$somevar = 10;
foo($somevar); // $somevar passed by reference
echo $somevar; // prints 20

You can also make functions return a reference by putting the & in front of the function name..

function &foo($bar) {
   return $something; // $something gets returned by reference
}