Class question. Where am I going wrong?

[Adam]

Hi everyone,

I figured by doing a larger project, I could start to learn how objects
and classes work in PHP, but I am running into a problem.

I am trying to write a sudoku generator. I was going to make a cell
class to hold the potential values of a cell...

class cell {
public $potentialValues = array(1,2,3,4,5,6,7,8,9);
}

Then a row class to hold and run functions of the cells in a row...

class row {
public $cell1 = new cell();
public $cell2 = new cell();
public $cell3 = new cell();
public $cell4 = new cell();
public $cell5 = new cell();
public $cell6 = new cell();
public $cell7 = new cell();
public $cell8 = new cell();
public $cell9 = new cell();
}

And finally a matrix class to hold all the rows...

class matrix {
public $row1 = &new row();
public $row2 = &new row();
public $row3 = &new row();
public $row4 = &new row();
public $row5 = &new row();
public $row6 = &new row();
public $row7 = &new row();
public $row8 = &new row();
public $row9 = &new row();
}

The problem is is that I guess I cannot use objects within another
class since this code errors. (Parse error: syntax error, unexpected
T_NEW in yadda/yadda/yadda.php). Could someone take a second to set me
right and kindly point me in the right direction? I have a feeling I
am just not looking at this problem correctly.

Thanks, Adam

[Mateusz Markowski]

Adam napisal(a):

class matrix {
public $row1 = &new row();
public $row2 = &new row();
public $row3 = &new row();
public $row4 = &new row();
public $row5 = &new row();
public $row6 = &new row();
public $row7 = &new row();
public $row8 = &new row();
public $row9 = &new row();
}

The problem is is that I guess I cannot use objects within another
class since this code errors. (Parse error: syntax error, unexpected
T_NEW in yadda/yadda/yadda.php). Could someone take a second to set me
right and kindly point me in the right direction? I have a feeling I
am just not looking at this problem correctly.

A default class property must be string, number or array. "new"
operator is not allowed.
Why are creating so many properties instead an array of them? Try:

class Matrix {
private $rows = array();
public function __construct($howmany)
{
for ($i=0;$i<$howmany;$i++) {
$this->rows[$i] =new Row();
}
}
}

[Adam]

Mateusz Markowski wrote:

Adam napisal(a):

class matrix {
public $row1 = &new row();
public $row2 = &new row();
public $row3 = &new row();
public $row4 = &new row();
public $row5 = &new row();
public $row6 = &new row();
public $row7 = &new row();
public $row8 = &new row();
public $row9 = &new row();
}

The problem is is that I guess I cannot use objects within another
class since this code errors. (Parse error: syntax error, unexpected
T_NEW in yadda/yadda/yadda.php). Could someone take a second to set me
right and kindly point me in the right direction? I have a feeling I
am just not looking at this problem correctly.

A default class property must be string, number or array. "new"
operator is not allowed.
Why are creating so many properties instead an array of them? Try:

class Matrix {
private $rows = array();
public function __construct($howmany)
{
for ($i=0;$i<$howmany;$i++) {
$this->rows[$i] =new Row();
}
}
}

I dont know why I am not using an array. I think I am getting confused
on objects and I am losing my mind :) What is the reasoning behind why
default class properties only being a string, number, or array? I think
knowing that would help me understand better. Thanks for your help
Mateusz!

[Colin Fine]

Adam wrote:

Mateusz Markowski wrote:

>Adam napisal(a):

>>class matrix {
public $row1 = &new row();
public $row2 = &new row();
public $row3 = &new row();
public $row4 = &new row();
public $row5 = &new row();
public $row6 = &new row();
public $row7 = &new row();
public $row8 = &new row();
public $row9 = &new row();
}

The problem is is that I guess I cannot use objects within another
class since this code errors. (Parse error: syntax error, unexpected
T_NEW in yadda/yadda/yadda.php). Could someone take a second to set me
right and kindly point me in the right direction? I have a feeling I
am just not looking at this problem correctly.

A default class property must be string, number or array. "new"
operator is not allowed.
Why are creating so many properties instead an array of them? Try:

class Matrix {
private $rows = array();
public function __construct($howmany)
{
for ($i=0;$i<$howmany;$i++) {
$this->rows[$i] =new Row();
}
}
}

I dont know why I am not using an array. I think I am getting confused
on objects and I am losing my mind :) What is the reasoning behind why
default class properties only being a string, number, or array? I think
knowing that would help me understand better. Thanks for your help
Mateusz!

The manual http://www.php.net/manual/en/language.oop5.basic.php actually
says:

"The default value must be a constant expression, not (for example) a
variable, a class member or a function call."

I don't know the reason, but I observe that this way, these initial
values will be the same in every instance of the class. If you were
allowed variables, function calls or new (which is a disguised function
call) they might have different values for every object of the class.

There's nothing wrong with this, but you can get that effect by setting
the value in the constructor, so it is useful to have variable
initialisation serving a different purpose.

Colin

[e_matthes]

I banged my head against the php wall for a while when I wrote my first
simple OOP program in php; all because I was using one underscore when
writing __construct rather than two! I am guessing this frustration
happens all the time, and I couldn't believe the book I was using did
not explicitly state this. Is there a reason it was specified with two
underscores?

Eric

[Jerry Stuckle]

Adam wrote:

Mateusz Markowski wrote:

>>Adam napisal(a):

>>>class matrix {
public $row1 = &new row();
public $row2 = &new row();
public $row3 = &new row();
public $row4 = &new row();
public $row5 = &new row();
public $row6 = &new row();
public $row7 = &new row();
public $row8 = &new row();
public $row9 = &new row();
}

The problem is is that I guess I cannot use objects within another
class since this code errors. (Parse error: syntax error, unexpected
T_NEW in yadda/yadda/yadda.php). Could someone take a second to set me
right and kindly point me in the right direction? I have a feeling I
am just not looking at this problem correctly.

A default class property must be string, number or array. "new"
operator is not allowed.
Why are creating so many properties instead an array of them? Try:

class Matrix {
private $rows = array();
public function __construct($howmany)
{
for ($i=0;$i<$howmany;$i++) {
$this->rows[$i] =new Row();
}
}
}

I dont know why I am not using an array. I think I am getting confused
on objects and I am losing my mind :) What is the reasoning behind why
default class properties only being a string, number, or array? I think
knowing that would help me understand better. Thanks for your help
Mateusz!

Default values must be constants. If you want to execute code as above,
simply put it in the constructor for the class. That's what it's
designed for.

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
js*******@attglobal.net
==================

[Snef]

e_*******@hotmail.com wrote:

I banged my head against the php wall for a while when I wrote my first
simple OOP program in php; all because I was using one underscore when
writing __construct rather than two! I am guessing this frustration
happens all the time, and I couldn't believe the book I was using did
not explicitly state this. Is there a reason it was specified with two
underscores?

Eric

Maybe because some people were using _xxx to emulate private properties/methods
when those where not available yet.

function _blaFoo() {}

Snef.