Mine

<?php

function circle_points($cx, $cy, $x, $y)
{
	if ($x == 0) {
		$points[] = array($cx, $cy + $y);
		$points[] = array($cx, $cy - $y);
		$points[] = array($cx + $y, $cy);
		$points[] = array($cx - $y, $cy);
	} else
	if ($x == $y) {
		$points[] = array( $cx + $x, $cy + $y);
		$points[] = array( $cx - $x, $cy + $y);
		$points[] = array( $cx + $x, $cy - $y);
		$points[] = array( $cx - $x, $cy - $y);
	} else
	if ($x < $y) {
		$points[] = array( $cx + $x, $cy + $y);
		$points[] = array( $cx - $x, $cy + $y);
		$points[] = array( $cx + $x, $cy - $y);
		$points[] = array( $cx - $x, $cy - $y);
		$points[] = array( $cx + $y, $cy + $x);
		$points[] = array( $cx - $y, $cy + $x);
		$points[] = array( $cx + $y, $cy - $x);
		$points[] = array( $cx - $y, $cy - $x);
	}
	return $points;
}

function circle_midpoint($xCenter, $yCenter, $radius)
{
	$x = 0;
	$y = $radius;
	$p = (5 - $radius*4)/4;

	$points = circle_points($xCenter, $yCenter, $x, $y);
	while ($x < $y) {
		$x++;
		if ($p < 0) {
			$p += 2*$x+1;
		} else {
			$y--;
			$p += 2*($x-$y)+1;
		}
		if (is_array($points2 = circle_points($xCenter, $yCenter, $x, $y))) {
			$points = array_merge($points,$points2);
		}
	}
	return $points;
}

function boundary_fill($x, $y, $width, $height, $points, &$area)
{
	if (($x < 0) || ($x >= $width)) return;
	if (($y < 0) || ($y >= $height)) return;
	$current = array_search(array($x,$y),$points);
	echo "$x,$y ";
	 //array search pixel
	if ($current === false) {
		echo "false\n";
		//raster.setPixel(fill, x, y);
		$area[] = array($x,$y);
		boundary_fill($x+1, $y, $width,$height, $points,$area);
		boundary_fill($x, $y+1, $width,$height, $points,$area);
		boundary_fill($x-1, $y, $width,$height, $points,$area);
		boundary_fill($x, $y-1, $width,$height, $points,$area);
	}else{
		echo "true\n";
	}
}

$im = imagecreatetruecolor(400, 400);
$points = circle_midpoint(10,100,50);
$color = imagecolorallocate($im, 255, 0, 0);
foreach ($points as $pixel){
	imagesetpixel($im,$pixel[0],$pixel[1],$color);
}
boundary_fill(10,100,400,400,$points,$area);
foreach ($area as $pixel){
	imagesetpixel($im,$pixel[0],$pixel[1],$color);
}
imagepng($im,'testing.png');

?>