[SOLVED] why =& ?

[sKunKbad]

I've been using php for about 3 years, and have never come across a script that used =& like the following example:

 

$foo =& new StdClass()

 

What does this do? How is it different than just plain =

[anupamsaha]

I've been using php for about 3 years, and have never come across a script that used =& like the following example:

 

$foo =& new StdClass()

 

What does this do? How is it different than just plain =

 

Its PHP 4 style. Not required in PHP5. In PHP5, call by reference is a default. You can omit the "&" sign.

 

[sKunKbad]

Its PHP 4 style. Not required in PHP5. In PHP5, call by reference is a default. You can omit the "&" sign.

 

OK, I have no sites using php4 anyway, but what was the reason to use =& anyways? I saw the docs on "return by reference", but I don't understand.

[KevinM1]

Its PHP 4 style. Not required in PHP5. In PHP5, call by reference is a default. You can omit the "&" sign.

 

OK, I have no sites using php4 anyway, but what was the reason to use =& anyways? I saw the docs on "return by reference", but I don't understand.

 

Normal assignment is often achieved with 'return by value.'  This means that a copy of the value is returned and stored in the variable being assigned to.  'Return by reference' actually stores a reference to that particular value/object/whatever.  So, instead of having a copy, you're essentially dealing with the real thing.

 

More info: http://www.adp-gmbh.ch/php/pass_by_reference.html , http://us2.php.net/references

[MadTechie]

okay i started to type this then i had a long phone call

 

 

Its the same idea as a pointer in C.

 

okey heres a function

 

<?php
$data = "123";
$data = addstuff($data);
function addstuff($add)
{
  $add = $add."Blar"
  return $add;
}
?>

 

Okay what that does is pass 123 and then returns 123456

Now the memory used is

$data = "123";

then

$data = "123";

$add= "123";

then

$data = "123";

$add= "123Blar";

then

$data = "123Blar";

 

okay.. now with Passing by Reference (not default in php 5)

<?php
$data = "123";
addstuff($data);
function addstuff(&$add)
{
  $add = $add."Blar"
}
?>

 

this is how it goes

$data = "123";

then

$data = "123"; and  $add= $data; these take up the same memory block so if $add changes then $data changed

then

$add= "123Blar"; //so $data = 123Blar

[sKunKbad]

MadTechie, thanks for the explanation. I understand now.

[MadTechie]

Welcome, as a note since PHP5 there is a little change, from what i said..

Now the memory used is

$data = "123";

then

$data = "123";

$add= "123"; <---In PHP4 this is true BUT in PHP5 this is still a referance BUT as soon as it changes it takes a new memory block, where as pass by ref will not create a new block

then

$data = "123";

$add= "123Blar";

then

$data = "123Blar";

 

Also please note that the function doesn't return anything and nothing gets set from the function,

 

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