Learning OOP

[jez_jez-d_co_uk]

After using PHP for close to two years, and being delighted with it, I have realised that I need to move forward and learn OOP.

I wrote a class to double a number inputted from a form, which looks like this:

<?php
class testclass {

public function double($demo) {
return $demo * 2;
}

}
?>

I then decided to try to be clever and insert a method to validate the data, prior to doubling the number. The idea was to have the new validation method call the 'double' method if all validates ok. I know I could call the method from the same script that the form is on, but I want to call it from within the class. I tried this but it didn't work:

<?php
class testclass {

public function validate($demo) {
if($demo!=''){
$this->double($demo);
}else {
return 'Please enter number';
}
}

public function double($demo) {
return $demo * 2;
}

}
?>

So, can someone tell me why it doesn't work and how to make it work? The validation part works ok, but it's not calling the 'double' function.

[Bjom]

works fine for me. Maybe you didn't use the class properly? have a look at how I used it.

ImHO you should make the "double" function call the validate function, not vice versa and make the double public; the validate private. Here is your class with proper indentation and how I called it:

class testclass {

public function validate($demo) {
	if($demo!=''){
		$this->double($demo);
	}else {
		return 'Please enter number';
	}
}

public function double($demo) {
	echo $demo * 2;
}

}


$tst = new testclass;
$result = $tst->validate(5); 
echo $result;

[jez_jez-d_co_uk]

Bjom;10933877 wrote:

Maybe you didn't use the class properly?

Hello Bjom,

You were right. I have also changed the script as per your advice and it now looks like this:

class testclass { 

private function validate($demo) { 
    if($demo==''){ 
       die ('Please enter number'); 
    } 
} 

public function double($demo) { 
    $this->validate($demo); 
   	return $demo * 2; 
} 

} 

<form action="<?php echo $_SERVER['PHP_SELF'];?>" method="post">
<input name="number" type="text" />
<input type="submit" value=" - Go - " />

</form>

if($_POST){
$number = $_POST['number'];
$tst = new testclass; 
$result = $tst->double($number); 
echo $result;
}

Vielen Dank für Ihre Hilfe

[NogDog]

While I realize this is just a learning script, a suggestion would be not to die() within the validation method. Instead leave that decision to the code that uses the class. Probably better would be to have it return true false, and let the method that calls it respond based on that result.

<?php
class testclass
{
   public function double($demo)
   {
      if($this->validate($demo))
      {
         return($demo * 2);
      }
      return false;
   }
   private function validate($demo)
   {
      return(!empty($demo) && is_numeric($demo));
   }
}

// Test cases:
$testData = array('', 'abc', 5, 7.5);
$test = new testclass();
foreach($testData as $value)
{
   $result = $test->double($value);
   if($result === false)
   {
      echo "Invalid value '$value'<br />\n";
   }
   else
   {
      echo "$value doubled = $result<br />\n";
   }
}

[Bjom]

Bitte, gern geschehen!

Nogdog's version is great - as always.