Proper code for calling my own function

[AndyB]

In the following code example, my function is not returning the modified variable:

<?php

class Andy_ConvertImage_DataWriter extends XFCP_Andy_ConvertImage_DataWriter
{
	public function preSave()
	{
		// make sure preSave() is only run once
		if ($this->_preSaveCalled)
		{
			return;
		}
		
		// define variables
		$newMessage = '';
		$myData = '';

		$newMessage = $this->get('message');
		
		$this->mainLoop($newMessage);
		
		$this->set('message', $myData);
		
		// call parent function
		parent::preSave();
	}
	
	public function mainLoop($newMessage)
	{
		$myData = $newMessage . 'testing';
		return $myData;
	}
}

?>

When I edit a post I should get the word "testing" added to the end of the message.

At this point the $newMessage variable is being passed into my function, but the variable $myData is not being passed back. What am I doing wrong?

Thank you.

 

[Jeremy]

You don't save the return of your function.

 

[AndyB]

You don't save the return of your function.

Hi Jeremy,

Thank you for looking at the code. Where should I look to fix this:

1) Add code to the mainLoop() function
2) Add code to the preSave() function

 

[KenSmith]

Probably this is what you meant:

$myData = $this->mainLoop($newMessage);

 

[AndyB]

Probably this is what you meant:

$myData = $this->mainLoop($newMessage);

I sure appreciate the help, Ken. That worked perfect!

<?php

class Andy_ConvertImage_DataWriter extends XFCP_Andy_ConvertImage_DataWriter
{
	public function preSave()
	{
		// make sure preSave() is only run once
		if ($this->_preSaveCalled)
		{
			return;
		}
		
		// define variables
		$newMessage = '';
		$myData = '';

		$newMessage = $this->get('message');
		
		$this->mainLoop($newMessage);
		
		$myData = $this->mainLoop($newMessage);
		
		$this->set('message', $myData);
		
		// call parent function
		parent::preSave();
	}
	
	public function mainLoop($newMessage)
	{
		$newMessage = $newMessage . 'testing';
		return $newMessage;
	}
}

?>

 

[Liam W]

No point in doing something without learning

$myData = $this->mainLoop($newMessage);

That lines stores the value returned from the mainLoop function into the $myData variable.

$this->mainLoop($newMessage);

That would call the mainLoop function, and discard any returned value.

 

[euantor]

No point in doing something without learning

$myData = $this->mainLoop($newMessage);

That lines stores the value returned from the mainLoop function into the $myData variable.

$this->mainLoop($newMessage);

That would call the mainLoop function, and discard any returned value.

Just to add to this, you could pass the variable by reference to the method too to achieve a similar result.

 

[Liam W]

Just to add to this, you could pass the variable by reference to the method too to achieve a similar result.

True, but that would probably confuse them

 

[Jeremy]

Passing by reference is a perfectly valid practice, Liam. Run time pass by reference is the bad practice and PHP now warns and or prevents on it.

 

[euantor]

@Jeremy that's interesting to know. Was that introduced in 5.5 or 5.4? I tend only to concentrate on the bigger changes between versions when reading the announcements.

 

[Jeremy]

5.4:
http://php.net/manual/en/language.references.pass.php

 

[euantor]

5.4:
http://php.net/manual/en/language.references.pass.php

Cheers. I've never noticed because I never even knew you could do it in the call in the first place. So used to doing it in the method declaration.

 

[Jeremy]

The method declaration is the proper use of a referenced variable, and it should have always been done there to make functions consistent between calls.

 

[euantor]

Of course it is, most languages only allow it in the declaration. There are very few I know of that allow it at call time.

 

[AndyB]

No point in doing something without learning

$myData = $this->mainLoop($newMessage);

That lines stores the value returned from the mainLoop function into the $myData variable.

$this->mainLoop($newMessage);

That would call the mainLoop function, and discard any returned value.

Thank you Liam,

I really appreciate you taking the time to explain the above.

So now I have the following code which works great:

<?php

class Andy_ConvertImage_DataWriter extends XFCP_Andy_ConvertImage_DataWriter
{
	public function preSave()
	{
		// make sure preSave() is only run once
		if ($this->_preSaveCalled)
		{
			return;
		}
		
		// define variables
		$newMessage = '';
		$myData = '';

		$newMessage = $this->get('message');
		
		$myData = $this->mainLoop($newMessage);
		
		$this->set('message', $myData);
		
		// call parent function
		parent::preSave();
	}
	
	public function mainLoop($newMessage)
	{
		$newMessage = $newMessage . 'testing';
		return $newMessage;
	}
}

?>