imagerotate has special intern functions when the rotation angle is a multiple of 90°, it actually only flips the image. The operation is quite fast as it is a two nested loops with a little copy operation. However it looks like the manual has a little mistake in the function description, which can lead to confusion:

"The center of rotation is the center of the image, and the rotated image is scaled down so that the whole rotated image fits in the destination image – the edges are not clipped."

<br />
$im = imagecreatefrompng(&#8220;foo.png&#8221;); <br />
imagepng($im, &#8220;2.png&#8221;);<br />
$imr = imagerotate($im, 90, 1, 1);<br />
imagepng($imr, &#8220;foo_90.png&#8221;);<br />
$imr = imagerotate($im, 180, 1, 1);<br />
imagepng($imr, &#8220;foo_180.png&#8221;); <br />
$imr = imagerotate($im, 270, 1, 1);<br />
imagepng($imr, &#8220;foo_270.png&#8221;); <br />
$imr = imagerotate($im, 30, 0&#215;000FF, 0);<br />
imagepng($imr, &#8220;foo_30.png&#8221;);<br />
 

Will return:

As you can see, as long as the rotation is only a flip (angle is a multiple of 90°), the image dimensions are preserved. If not, the final image will have the exact size required by the rotated image. I hope it is clearer now, I will try to update the manual as soon as possible. Thanks to the phpdoc team, I can now put all kind of psychedelic images in there!