OO PHP Referencing an instance of a class

[Areric]

Ok all im havign some issues with a class im writing was hoping you all
could help. I dont have access to the actual code here but ill write
out an example of what im trying to do and maybe you all could provide
some pointers.

1: class Foo
2: {
3: $mInstanceBar;
4:
5: function __construct()
6: {
7: $this->mInstanceBar = & new Bar();
8: }
9:
10: function callBarHelloWorld()
11: {
12: $this->mInstanceBar->HelloWorld();
13: }
14: }
15:
16: class Bar
17: {
18: function HelloWorld()
19: {
20: echo "Hello World!";
21: }
22: }
23: $foo = new Foo();
24: $foo->callBarHelloWorld();

Ok line 12 returns an error saying something to the effect that im
calling a function on something that is not an object.

My impression was that on line 7 i am instantiating the object as a
reference which should still be available when called on line 12.

So any ideas?

[David Haynes]

Areric wrote:

Ok all im havign some issues with a class im writing was hoping you all
could help. I dont have access to the actual code here but ill write
out an example of what im trying to do and maybe you all could provide
some pointers.

1: class Foo
2: {
3: $mInstanceBar; private $mInstanceBar; 4:
5: function __construct()
6: {
7: $this->mInstanceBar = & new Bar(); $this->mInstancebar = new Bar(); 8: }
9:
10: function callBarHelloWorld()
11: {
12: $this->mInstanceBar->HelloWorld();
13: }
14: }
15:
16: class Bar
17: {
18: function HelloWorld()
19: {
20: echo "Hello World!";
21: }
22: }
23: $foo = new Foo();
24: $foo->callBarHelloWorld();

Ok line 12 returns an error saying something to the effect that im
calling a function on something that is not an object.

My impression was that on line 7 i am instantiating the object as a
reference which should still be available when called on line 12.

So any ideas?

[Areric]

SO what is the point of the &. I tried that option as well and was told
on another site i should use & to make a reference to the class?

[Justin Koivisto]

Areric wrote:

Ok all im havign some issues with a class im writing was hoping you all
could help. I dont have access to the actual code here but ill write
out an example of what im trying to do and maybe you all could provide
some pointers.
<snip>
So any ideas?

PHP5 is so nice for this kind of thing...

<?php
class Foo {
private $subObj = NULL;

public function __construct(){
// create an instance of the class we want to use in here
$this->subObj = new Bar();
}

public function __call($method,$args){
// this method is called if we attempt to call a method that is
// not declared in the class definition
if(method_exists($this->subObj,$method)){
return $this->subObj->$method($args);
}else{
echo 'Method does not exist: ',$method;
return FALSE;
}
}

public function fooWorld($string){
echo "<p>Foo: $string</p>\n";
return TRUE;
}
}

class Bar {
public function BarWorld($string){
// since __call will send the method parameters as an array as
// above, we want to compensate for that case as well. May be better
// design to expect an array of parameters to begin with(?)
if(is_array($string)){
$string=join($string);
}
echo "<p>Bar: $string</p>\n";
return TRUE;
}
}

$foo = new Foo();

$foo->fooWorld('Foo string');
$foo->barWorld('Bar string');

/*
OUTPUT:
<p>Foo: Foo string</p>
<p>Bar: Bar string</p>
*/
?>

See:
http://www.php.net/manual/en/languag...verloading.php

HTH
--
Justin Koivisto, ZCE - ju****@koivi.com
http://koivi.com

[David Haynes]

Areric wrote:

SO what is the point of the &. I tried that option as well and was told
on another site i should use & to make a reference to the class?

Think of '&' as 'address of'.

So $bar = & new Bar();

is '$bar equals the address of the instance of the class Bar'

To use it, you would have to dereference it twice (once to resolve the
reference and once to resolve the instance).

So if Bar had a method foo(), you would access it as:

$$bar->foo();

As Justin points out, if you really want to use reference to instances
and not just instances, then there is loads of support in PHP5.

-david-

[Janwillem Borleffs]

Areric wrote:

5: function __construct()
6: {
7: $this->mInstanceBar = & new Bar();
8: }
9:

The __construct() method is not supported by PHP < 5. In this case, the
constructor should be called Foo().
JW

[Janwillem Borleffs]

Janwillem Borleffs wrote:

The __construct() method is not supported by PHP < 5. In this case,
the constructor should be called Foo().

Or, to make your class cross-compatibe, add the following method:

function Foo() {
$this->__construct();
}
JW

[Areric]

Ok that could be it. Im using PHP4 at the moment (shared hosting,
unfortuantly not my choice). Also In response to David above that makes
sense. PHP Takes a very c/c++ approach to classes almost.

Ill try out all of your suggestions and maybe ill set up my spare
machine with php5 and run a 5 version. I really would like to have
access to public / private / protected members as well as interfaces
which from what i understand PHP5 supports.

Im trying to make what im writing very OO-Principle based, including
polymorphism, which implys, to some extent, interfaces.

[Areric]

OK all. Still having issues im going to copy the real code this time
since i have access to it.

class ImageModifierTest //implements ITest
{
var $imageModifier = NULL;
var $testHelpers = NULL;
function __construct()
{
$imageModifier = new ImageModifier();
$testHelpers = new TestHelpers();
}

function ImageModifierTest()
{
$this->__construct();
}

function TestOpenBinaryStream()
{
$streamToSend = "111010001010001";
return $this->imageModifier->OpenBinaryStream($streamToSend);
//THE ABOVE LINE IS WHERE IT ERRORS
return $this->testHelpers->AssertAreEqual($binaryStream,
$streamToSend);
}
function GetBinaryStreamFromFile()
{

$this->imageModifier->SetImageFile('/srv/www/htdocs/images/testpng.png');
$this->imageModifier->CreateBinaryStreamFromFile();
return
$this->testHelpers->AssertIsNotEmpty($this->imageModifier->GetBinaryImageStream);
}
function ExecuteTests()
{
$success = ($this->TestOpenBinaryStream()) &&
($this->GetBinaryStreamFromFile());
if ($success == true)
{
return "Success";
}
else
{
return "Failure";
}
}
}

class ImageModifier
{
//MEMBERS
var $mImage = "";
var $mModifiedImage = "";
var $mBinaryImageStream = "";

function __construct()
{
}

function SetImageFile($image)
{
$this->mImage = $image;
}

function OpenBinaryStream($stream)
{
$this->mImage = $stream;
$this->mBinaryImageStream = $stream;
return $this->mImage;
}

function CreateBinaryStreamFromFile()
{
$fp = fopen($this->mImage, 'rb');
header("Content-Type: image/png");
header("Content-Length: " . filesize($this->mImage));
$this->mBinaryImageStream = file_get_contents($this->mImage);
}

function GetBinaryImageStream()
{
return $this->mBinaryImageStream;
}
}
Note i converted my __construct to the method suggested above. I also
got rid of the &s. Im using PHP4 at the moment.

[Areric]

did a little more testing and the __constructor thing didnt matter, it
got into there regardless of what i named it (class name or
__construct)

What i am finding is that my $imageModifier is still NULL when i get
into the test function. I put in a if ($imageModifier == NULL) echo
"ERROR"; and it does indeed print out error.

So any idea why when i KNOW its calling those NEW's in the constructor
it isnt keeping the values once it gets to the function that uses them.

[Areric]

OK all im dumb. i keep forgetting the $this-> stuff in PHP. Im used to
just using the member variable name.