Description:
------------
Imagepng() works in sample.php but doesn't work if same code is called inside function.

See reproduced code..

No errors, but it shows the broken image (like broken link to image or image doesn't exists)


Reproduce code:
---------------
sample.php
---
header('Content-type: image/png');
$this->image = "images/1.png";
$this->im=imagecreatefrompng($this->image);
$this->w=imagecolorallocate($this->im, 0, 0, 0);
imagepng($this->im);
imagedestroy($this->im);  
---

function show_image() {
	header('Content-type: image/png');
	$this->image = "images/1.png";
	$this->im=imagecreatefrompng($this->image);
	$this->w=imagecolorallocate($this->im, 0, 0, 0);
	imagepng($this->im);
        imagedestroy($this->im);  
}