Image rotate losing transparency

[tobeyt23]

I have the following code, works rotates the image. But it seems to lose its transparency and add color when rotated to say 45. How can I avoid this?

 

// File and rotation
$filename = 'placeholder.png';
$degrees = 45;

// Content type
header('Content-type: image/png');

// Load
$source = imagecreatefrompng($filename);


// Rotate
$rotate = imagerotate($source, $degrees, 0);

// Output
imagepng($rotate);
?>

[tobeyt23]

To explain if rotate id 90 or 180 it works perfectly, however if i do say 45 then it rotates but adds a black box around where it should be transparent