test.php:
<?php
header("Content-type: image/png");
$p = new Graph(500,200);
$p->addBorder("black");
$p->renderImage();
?>


graph.php:
<?php
class Graph {

	public function Graph($x_size, $y_size) {
		$this->im = imagecreate($x_size, $y_size);
		$this->x_size = $x_size;
		$this->y_size = $y_size;
	}

	public function addBorder($color) {
		imageline($this->im, 0, 0, $this->x_size, 0, getColor($color));
		imageline($this->im, $this->x_size, 0, $this->x_size, $this->y_size, getColor($color));
		imageline($this->im, $this->x_size, $this->y_size, 0, $this->y_size, getColor($color));
		imageline($this->im, 0, $this->y_size, 0, 0, getColor($color));
	}

	public function renderImage() {
		imagepng($this->im);
		imagedestroy($this->im);
	}
}
?>