Graph Generation Script - I think I've got my class format wrong!

[NickToony]

Hello,

 

I am using a tutorial script for generating a basic bar graph. I have attempted to convert this script into an object-oriented script. However, upon attempting to define the graph, it is not successfully generated. Here is my code:

 

<?

class Graph
{
	var $values;
	var $image;
	var $image_width = 450;
	var $image_height = 300;
	var $margin = 20;
	var $bar_size = 20;
	var $horizontal_lines = 20;

	var $bar_colour;
	var $border_colour;
	var $background_colour;
	var $line_colour;

	function CreateGraph()
		{
			$this->image = imagecreate($this->image_width, $this->image_height);
		}

	function SetSize($width, $height)
		{
			$this->image_width = $width;
        			$this->image_height = $height;
        		}
        	
        	function SetMargin($size)
        		{
        			$this->margin = $size;
        		}
        		
        	function SetBarSize($size)
        		{
        			$this->bar_size = $size;
        		}
        		
        	function SetHorLines($size)
        		{
        			$this->horizontal_lines = $size;
        		}
        		
        	function HexConvert($rgb) 
        		{
    			return array(
			        base_convert(substr($rgb, 0, 2), 16, 10),
			        base_convert(substr($rgb, 2, 2), 16, 10),
			        base_convert(substr($rgb, 4, 2), 16, 10),
			    );
		}
        	
        	function SetColours($bars, $background, $border, $line)
        		{
        			// This is hex based, similar to CSS, it is converted by HexConvert
        			$bars = $this->HexConvert($bars);
        			$background= $this->HexConvert($background);
        			$border= $this->HexConvert($border);
        			$line = $this->HexConvert($line);
        			
        			$this->bar_colour = imagecolorallocate($this->image, $bars[0], $bars[1], $bars[2]);
        			$this->background_colour = imagecolorallocate($this->image, $background[0], $background[1], $background[2]);
        			$this->border_colour = imagecolorallocate($this->image, $border[0], $border[1], $border[2]);
        			$this->line_colour =imagecolorallocate($this->image, $line [0], $line [1], $line [2]);
        		}
        	
        	function DrawBorders()
        		{
        			imagefilledrectangle($this->image,1,1,$this->image_width-2,$this->image_height-2,$this->border_colour);
			imagefilledrectangle($this->image,$this->margin,$this->margin,$this->image_width-1-$this->margin,$this->image_height-1-$this->margin,$this->background_colour);
		}

	function DrawHorLines($horizontal_gap, $ratio)
		{
			for($i=1;$i<=$this->horizontal_lines;$i++)
				{
					$y = $this->image_height - $this->margin - $horizontal_gap * $i ;
					imageline($this->image, $this->margin, $y, $this->image_width - $this->margin, $y, $this->line_colour);
					$v = intval($horizontal_gap * $i / $ratio);
					imagestring($this->image, 0, 5, $y-5, $v, $this->bar_colour);
				}
		}

	function DrawBars($graph_height, $gap, $ratio)
		{
			for($i=0;$i< $total_bars; $i++)
				{ 
					list($key,$value)=each($this->values); 
					$x1= $this->margin + $gap + $i * ($gap+$this->bar_size) ;
					$x2= $x1 + $this->bar_size;
					$y1 = $this->margin +$graph_height- intval($value * $ratio) ;
					$y2 = $this->image_height-$this->margin;
					imagestring($this->image,0,$x1+3,$y1-10,$value,$this->bar_colour);
					imagestring($this->image,0,$x1+3,$this->image_height-15,$key,$this->bar_colour);		
					imagefilledrectangle($this->image,$x1,$y1,$x2,$y2,$this->bar_colour);
				}
		}
        	
        	function DrawGraph()
        		{
        			$graph_width=$this->image_width - $this->margin * 2;
			$graph_height=$this->image_height - $this->margin * 2; 

			$total_bars  = count($values);
			$gap = ($graph_width- $total_bars * $this->bar_width ) / ($total_bars +1);

			$this->DrawBorders();

			$max_value=max($values);
			$ratio = $graph_height / $max_value;

			$horizontal_gap = $graph_height / $horizontal_lines;

			$this->DrawHorLines($horizontal_gap, $ratio);

			$this->DrawBars($graph_height, $gap, $ratio);
		}

	function OutputGraph()
		{
			header("Content-type:image/png");
			imagepng($this->image);
		}
}

?>

 

I expect this to be my misunderstanding of how object orientated codes work. I'm also open to any suggestions for improvement.

 

Edit: Here is the script where I use the class.

<?
include "bargraph.class.php";

$graph = new Graph;
$graph->SetSize(450, 300);
$graph->CreateGraph();
$graph->SetMargin(20);
$graph->SetBarSize(20);
$graph->SetHorLines(20);
$graph->SetColours("FFFFFF", "C0C0C0", "000000", "000000");
$graph->DrawGraph();
$graph->OutputGraph();
?>