[RESOLVED] Beginning Classes 101

Dawg

I am reading my books and trying to learn how to write classes. Why, because I know it will be much easier in the future to develop things in general.

SO below is the html page and the class. I am trying to just call a basic class and return a string variable to display. But All I get is "OBJECT"

What is wrong?

<?PHP

include("./includes/archive_class.php");

$display = new article_archive();

?>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body>

  <table width="600" align="center" cellpadding="5" cellspacing="5">
    <tr>
      <td>
		  <div align="Center" style="font-size:x-large"><?PHP echo $display; ?> </div>
	  </td>
    </tr>
  </table>
</div>
</body>
</html>

Class

class article_archive
{

function article_archive()

	{
		$string = "Function  found";
		return $string;
	}
}

I have tried returning $this->$string and other variations but I am not getting anyhwere.

I think I need a better book to reference than my old PHP4 Bible.

Thanks

bradgrafelman

At this point, $display is simply an instance of an object (as PHP told you). To actually do something with this object, e.g. get the output of the article_archive() function, try this:

$display = new article_archive;
echo $display->article_archive();

Alternatively, if you don't want to create an instance of an object, but simply call a function within the class, you could do:

echo article_archive::article_archive()

Dawg

Thanks Brad, What I eventually want to do is have my own class for connecting to the DB and either Inserting, Updating or Deleting records.

The class code is a bit different to deal with. and books don't always make things very clear.

After you create a new instance of an a class, how do you kill it??

Here is the output from your suggestion

class article_archive { function article_archive() { $string = "Function connect() found"; return $string; } }

bradgrafelman

Dawg wrote:
After you create a new instance of an a class, how do you kill it??

Well there's not normally any need to destroy the instance manually, but you could do a simple [man]unset/man to destroy it.

Dawg

I can't seem to get it to return anything. Are classes not good for returning data?

It is just a simple class like I posted above but I can't get it to return usable data to display in a web page.

Maybe I just don't understand.

NogDog

The class either needs a method that will return something, or a class variable that you can access.

class Example
{
   public $var1;
   private $var2;

   public function setVar2($val)
   {
      $this->var2 = $val;
   }

   public function getVar2()
   {
      return $this->var2;
   }
}

$test = new Example();
$test->var1 = 'foo'; // directly set public variable
$test->setVar2('bar'); // use setter method for private variable
echo $test->var1;  // directly reference public variable
echo $test->getVar2();  // use getter method for private variable

Dawg

The web page works fine until I try an instantiate the class.
Web page:

<?PHP

include("/includes/archive_class.php");

$test1 = new article_archive();
$display = $test1->test(); 


?>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link href="/css/CSS.css" rel="stylesheet" type="text/css" />
<link href="/css/layout.css" rel="stylesheet" type="text/css" />
</head>
<body>

<div id="wrapper">

<div id="header">
	<?php include("index_header.inc"); ?>
</div>

<div id="separator">
<center>
	<?php include("menu.inc"); ?>
</center>
</div>

  <table width="600" align="center" cellpadding="5" cellspacing="5">
    <tr>
      <td>
		  <div align="Center" style="font-size:x-large">HELLO<br /><?PHP echo $display;  ?> </div>
	  </td>
    </tr>
  </table>

	<div id="footer">
		<?PHP include("index_footer.inc"); ?>
	</div>

</div>
</body>
</html>

Class:

<?PHP

class article_archive
{
	public $string;

public function test()

	{
		$string = "Class/Function()  found";

		return $this->$string;
	}
}

?>

NogDog

<?PHP

class article_archive
{
    public $string;

public function test()

    {
        $this->string = "Class/Function()  found"; // added "$this->"

        return $this->string; // no "$" before "string"
    }
}

?>

PS: Turning on all error reporting might help you detect these things, if you haven't done so already. You can set it locally in the script with:

<?php
ini_set('display_errors', 1);
error_reporting(E_ALL);

Dawg

Ther error that is returned is:

Parse error: syntax error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in /path/archive_class.php on line 6

Line one of the actual code is blank, <?PHP is on line 2.

<?PHP

class article_archive
{
    public $string;

public function test()

    {
        $this->string = "Class/Function()  found"; // added "$this->"

        return $this->string; // no "$" before "string"
    }
}

?>

bradgrafelman

PHP4 or 5?

Dawg

PHP 4.4.7

bradgrafelman

Ah, ancient software that I don't have with me on my laptop, in other words. :p

Try changing the variable name to something different, like private $myString and see if that works?

Dawg

Same error.

Parse error: syntax error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in /includes/archive_class.php on line 6

From my understanding, reporting an error on line 6, I have been told will actually mean to look to the previous line for the error. Line 6 of the code is the public variable declaration.


<?PHP

class article_archive
{
    public $mystring;

public function test()

    {
        $this->mystring = "Class/Function()  found"; // added "$this->"

        return $this->mystring; // no "$" before "string"
    }
}

?>

bradgrafelman

D'oh, I'm dumb. Try changing "public" to "var" on the variable declaration line. I don't believe PHP4 supports public/private/etc. variable declarations ([man]OOP[/man] vs. [man]OOP5[/man] in the manual).

Dawg wrote:
From my understanding, reporting an error on line 6, I have been told will actually mean to look to the previous line for the error.

Not necessarily; for parse errors, the next line usually contains some syntax that finall triggers the error. Since PHP4 immediately saw something it didn't recognize (public keyword + variable declaration) it immediately triggered a parse error. It just depends.

Dawg

YEP, I had to remove all public / private declarations. Then it worked

Now I can actually go on and try to write a real class

<?PHP

class article_archive
{
    var $mystring;

function test()

    {
        $this->mystring = "Class/Function()  found"; // added "$this->"

        return $this->mystring; // no "$" before "string"
    }
}

?>

Thanks

NogDog

And try to get on a host/server situation where you can use PHP5. It's OOP support is much better; and besides, PHP4 is dead and within the next month they will not even be releasing any security patches for it any more.

Dawg

I'll have to look into it.

I knew it was something simple, which usually makes it hard to see.

Thanks for the help.