Just because the file is 0 bytes doesn't mean your template isn't working. var_dump() the contents of $data and see if there's anything in it. If there is, then your problem is in the file_put_contents() function.

It's probably easier to test the rendering using a function in your controller.. like:

public function pageflip(){
	return $this->renderWith('PageFlipXML);
}

Then you should be able to open yoursite.tld/page/pageflip to get the xml output (for testing or direct usage in flash).

When i hit save in the DOM i see this for a short second.

string(0) ""

Redirecting to http://www.url.nl/admin/EditForm/field/FlyerPaginas/item/18/edit?ctf[FlyerPaginas][start]=0&ctf[FlyerPaginas][per_page]=10&ctf[FlyerPaginas][showall]=0&ctf[FlyerPaginas][sort]=&ctf[FlyerPaginas][sort_dir]=&ctf[FlyerPaginas][search]=&ctf[FlyerPaginas][filter]=&ctf[FlyerPaginas][view]=... (output started on /public/sites/www.url.nl/mysite/code/Flyer.php, line 62)

line 62 = var_dump ($data);
So string(0) "" means there's nothing rendered?

Ok it is giving me a nice page WITH xml content

<book plugins="anchors, backgroundsounds, batchpages, bookmarks, console, gallery, help, javascript, keyboardnavigation, links, navigationbar, options, overlays, pdflinks, print, slideshow, swfaddress, titles">
<foreground>
	</foreground>
−
<chapter>
−
<page>
<img src="/assets/Uploads/abcdef.jpg"/>
</page>
−
<page>
<img src="/assets/Uploads/abcdef1.jpg"/>
</page>
−
<page>
<img src="/assets/Uploads/abcdef2.jpg"/>
</page>
−
<page>
<img src="/assets/Uploads/abcdef3.jpg"/>
</page>
−
<page>
<img src="/assets/Uploads/abcdef4.jpg"/>
</page>
−
<page>
<img src="/assets/Uploads/abcdef5.jpg"/>
</page>
−
<page>
<img src="/assets/Uploads/abcdef6.jpg"/>
</page>
</chapter>
</book>

How would i get this data to my file?

When i tried this:

	protected function onAfterWrite(){
	   parent::onAfterWrite();

		$data = $this->renderWith('PageFlipXML');	
		$ourFileName = "/public/sites/www.url.nl/pageflip/megazine/megazine.mz3";
		$fh = fopen($ourFileName, 'w+') or die("Can't open file");
		fwrite($fh, $data);
		fclose($fh);    
	}

it does write something.. 452 bytes file with the content:

<book plugins="anchors, backgroundsounds, batchpages, bookmarks, console, gallery, help, javascript, keyboardnavigation, links, navigationbar, options, overlays, pdflinks, print, slideshow, swfaddress, titles">
<foreground>
	</foreground>
−
<chapter>
−
    <page>
        <img src=""/>
    </page>
    
</chapter>
</book>

So i seems it isnt processing the template correctly?

When i go to the public function url:

www.url.nl/Flyer/pageflip

i do get all src's in the img tags..
How do i get the correct template data to the file?

thx!

Make sure FlyerPaginas is a function of your Page class, not the controller. Because the $this pointer in onAfterWrite isn't the controller, but just the page class (therefore you can't use any functions from the controller).

no change in the file write process.. still get a 0bytes file.

what am i doing wrong?

There must be a way to create a xml file with a onafterwrite() using a template. What code do you use?

<?php

class Flyer extends Page {

	static $has_many = array (
		'FlyerPaginas' => 'FlyerPagina'
	);
	
	public function getCMSFields() {
    $fields = parent::getCMSFields();
    $manager = new FileDataObjectManager(
      $this,
      'FlyerPaginas', // relation name
      'FlyerPagina', // class name of the DataObject
      'Image', // name of the file relation in the DataObject
      array(
			 'Title' => 'Title',
			// 'Comment' => 'Comment',
	 	), // headings
      'getCMSFields_forPopup' // name of the function for the popup fields
    
    );

	$fields->removeFieldFromTab('Root.Content.Main','Content');
	$fields->addFieldToTab('Root.Content.Images', $manager);
    return $fields;
  }
	public function megazine(){
	   return $this->renderWith('PageFlipXML');
	}	

}

class Flyer_Controller extends Page_Controller {

}

class FlyerPagina extends DataObject {

	static $db = array (
		'Title' => 'Text',
	//	'Comment' => 'HTMLText',
	);
	static $has_one = array (
		'Image' => 'Image',
		'Flyer' => 'Flyer'
	);

	public function getCMSFields_forPopup() {
		$fields = new FieldSet();
		//$fields->push(new TextField('Title'));
		//$fields->push(new SimpleTinyMCEField('Comment'));
		$fields->push(new FileUploadField('Image','Upload files'));
		return $fields;
	}
	
	protected function onAfterWrite(){
	   parent::onAfterWrite();
		$data = $this->renderWith('PageFlipXML');
		file_put_contents('/public/sites/www.url.nl/pageflip/megazine/PageFlipXML.mz3', $data);
	}
	


}

template code:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE book SYSTEM "http://www.megazine3.de/megazine2.dtd"> 
  
<book plugins="zoom, keyboardnavigation, navigationbar, swfaddress" 
lang="en"	
pagewidth="567" pageheight="567"  
	errorlevel="ERROR" 
	zoomminscale="0.5" zoommaxscale="4.0" 
	zoomsnap="0.5, 0.75, 1.0, 1.5, 2.0, 3.0, 4.0" 
	zoomsteps="2" 
	dragrange="20" 
	maxloaded="32" 
	qualitycontrol="true" 
	thumbscale="0.5" 
	searchmethod="client" 
	cornerhint="true" 
	pagethickness="0.2" 
	shadows="0.3" 
	searchclear="false" 
	startpage="1" 
	centercovers="false" 
	pageoffset="0">     
    
    
<!-- With zoomstep= "0.05" these zoom steps are achieved:  1.0 - 2.0 - 3.0 - 4.0 - ... 19.0 - 20.0 - 21.0 
	reason: the span (zoommaxscale-zoomminscale) is devided into 1/zoomstep (i.e. 20) intervals
	So span*zoomstep=1.0,  which results in a nice step size of 1.0--> 


	<foreground>
	</foreground>
	<chapter>
    
    <% control FlyerPaginas %>
		<page>
               <% control Image %><img src="$setWidth(2362).Link" scale="1" width="567" height="567"><% end_control %>
        </page>
        
    <% end_control %>
    
	</chapter>
</book>

Obviously, the onAfterWrite method should be in your Flyer page.. Or you leave it in FlyerPagina (if you want to write/update the file whenever a FlyerPagina is saved), but then your onAfterWrite method must look like this:

protected function onAfterWrite(){
	parent::onAfterWrite();
	if($this->FlyerID){
		$data = $this->Flyer->renderWith('PageFlipXML');
		file_put_contents('/public/sites/www.url.nl/pageflip/megazine/PageFlipXML.mz3', $data);
	}
}

and if file_put_contents doesn't work on your system, then use the fwrite function..

Update
You should always check if there's a Flyer.. so I updated the onAfterWrite function above..