Hi, I've rewrote function to class with static methods. Advantage of this solution is ability to be called several times during script execution.

<?php
/*
    Unfinished imagerotate replacement. ignore_transparent is, well, ignored. :)
    Also, should have some standard functions for 90, 180 and 270 degrees, since they are quite
    easy to implement faster.
*/

if(!function_exists("imagerotate")) {
    function imagerotate(&$srcImg, $angle, $bgcolor, $ignore_transparent = 0) {
        return imagerotateEquivalent::rotate(&$srcImg, $angle, $bgcolor, $ignore_transparent);
    }
}

class imagerotateEquivalent {

    static private function rotateX($x, $y, $theta){
        return $x * cos($theta) - $y * sin($theta);
    }

    static private function rotateY($x, $y, $theta){
        return $x * sin($theta) + $y * cos($theta);
    }

    public static function rotate(&$srcImg, $angle, $bgcolor, $ignore_transparent = 0) {
        
        $srcw = imagesx($srcImg);
        $srch = imagesy($srcImg);

        if($angle == 0) return $srcImg;

        // Convert the angle to radians
        $theta = deg2rad ($angle);

        // Calculate the width of the destination image.
        $temp = array (    self::rotateX(0,     0, 0-$theta),
                        self::rotateX($srcw, 0, 0-$theta),
                        self::rotateX(0,     $srch, 0-$theta),
                        self::rotateX($srcw, $srch, 0-$theta)
                    );
        $minX = floor(min($temp));
        $maxX = ceil(max($temp));
        $width = $maxX - $minX;

        // Calculate the height of the destination image.
        $temp = array (    self::rotateY(0,     0, 0-$theta),
                        self::rotateY($srcw, 0, 0-$theta),
                        self::rotateY(0,     $srch, 0-$theta),
                        self::rotateY($srcw, $srch, 0-$theta)
                    );
        $minY = floor(min($temp));
        $maxY = ceil(max($temp));
        $height = $maxY - $minY;

        $destimg = imagecreatetruecolor($width, $height);
        imagefill($destimg, 0, 0, imagecolorallocate($destimg, 0,255, 0));

        // sets all pixels in the new image
        for($x=$minX;$x<$maxX;$x++) {
            for($y=$minY;$y<$maxY;$y++)
            {
                // fetch corresponding pixel from the source image
                $srcX = round(self::rotateX($x, $y, $theta));
                $srcY = round(self::rotateY($x, $y, $theta));
                if($srcX >= 0 && $srcX < $srcw && $srcY >= 0 && $srcY < $srch)
                {
                    $color = imagecolorat($srcImg, $srcX, $srcY );
                }
                else
                {
                    $color = $bgcolor;
                }
                imagesetpixel($destimg, $x-$minX, $y-$minY, $color);
            }
        }
        return $destimg;
    }
}

?>