Make a graph in PHP

http://bit.ly/sLX1O4

http://bit.ly/sLX1O4

<?php
	@ $db=mysql_connect('localhost','root','mypass');
if(!$db)
{
echo 'ERROR:could not connect to database';
exit;
}
/*else
{
echo 'connection successful';
}*/
mysql_select_db('cdac',$db);
$query="select Class_Remarks from PGDASDD27 where module_name='DATA_STRUCTURES' AND Class_Remarks=(select MAX(Class_Remarks) from PGDASDD27 where module_name='DATA_STRUCTURES' AND Class_Remarks in(select Class_Remarks from PGDASDD27 where module_name='DATA_STRUCTURES' and Class_Remarks <(SELECT MAX(Class_Remarks)from PGDASDD27 where module_name='DATA_STRUCTURES')))";
$result=mysql_query($query);
$query="select Class_Remarks from PGDASDD27 where module_name='C++' AND Class_Remarks=(select MAX(Class_Remarks) from PGDASDD27 where module_name='C++' AND Class_Remarks in(select Class_Remarks from PGDASDD27 where module_name='C++' and Class_Remarks <(SELECT MAX(Class_Remarks)from PGDASDD27 where module_name='C++')))";
$result1=mysql_query($query);
$query="select Class_Remarks from PGDASDD27 where module_name='SQL_PL/SQL' AND Class_Remarks=(select MAX(Class_Remarks) from PGDASDD27 where module_name='SQL_PL/SQL' AND Class_Remarks in(select Class_Remarks from PGDASDD27 where module_name='SQL_PL/SQL' and Class_Remarks <(SELECT MAX(Class_Remarks)from PGDASDD27 where module_name='SQL_PL/SQL')))";
$result2=mysql_query($query);
$query="select Class_Remarks from PGDASDD27 where module_name='GENERAL APTITUDE' AND Class_Remarks=(select MAX(Class_Remarks) from PGDASDD27 where module_name='GENERAL APTITUDE' AND Class_Remarks in(select Class_Remarks from PGDASDD27 where module_name='GENERAL APTITUDE' and Class_Remarks <(SELECT MAX(Class_Remarks)from PGDASDD27 where module_name='GENERAL APTITUDE')))";
$result3=mysql_query($query);
//echo '<p>'.$query.'</p>';

	$values=array(
		"C++" => $result1*10,
		"DATA_STRUCTURES" => $result*10,
		"SQL" =>$result2*10 ,
		"GENERAL_APTITUDE" => $result3*10
	);

 
	$img_width=800;
	$img_height=600; 
	$margins=20;

 
	# ---- Find the size of graph by substracting the size of borders
	$graph_width=$img_width - $margins * 2;
	$graph_height=$img_height - $margins * 2; 
	$img=imagecreate($img_width,$img_height);
	
    
	
	$bar_width=20;
	$total_bars=count($values);
	$gap= ($graph_width- $total_bars * $bar_width ) / ($total_bars +1);

 
	# -------  Define Colors ----------------
	$bar_color=imagecolorallocate($img,0,64,128);
	$background_color=imagecolorallocate($img,240,240,255);
	$border_color=imagecolorallocate($img,200,200,200);
	$line_color=imagecolorallocate($img,220,220,220);
 
	# ------ Create the border around the graph ------

	imagefilledrectangle($img,1,1,$img_width-2,$img_height-2,$border_color);
	imagefilledrectangle($img,$margins,$margins,$img_width-1-$margins,$img_height-1-$margins,$background_color);

 
	# ------- Max value is required to adjust the scale	-------
	$max_value=56;//max($values);
	$ratio= $graph_height/$max_value;

 
	# -------- Create scale and draw horizontal lines  --------
	$horizontal_lines=5;
	$horizontal_gap=$graph_height/$horizontal_lines;

	for($i=1;$i<=$horizontal_lines;$i++){
		$y=$img_height - $margins - $horizontal_gap * $i ;
		imageline($img,$margins,$y,$img_width-$margins,$y,$line_color);
		$v=intval($horizontal_gap * $i /$ratio);
		imagestring($img,0,5,$y-5,$v,$bar_color);

	}
 
 
	# ----------- Draw the bars here ------
	for($i=0;$i< $total_bars; $i++){ 
		# ------ Extract key and value pair from the current pointer position
		list($key,$value)=each($values); 
		$x1= $margins + $gap + $i * ($gap+$bar_width) ;
		$x2= $x1 + $bar_width; 
		$y1=$margins +$graph_height- intval($value * $ratio) ;
		$y2=$img_height-$margins;
		imagestring($img,0,$x1+3,$y1-10,$value,$bar_color);
		imagestring($img,0,$x1+3,$img_height-15,$key,$bar_color);		
		imagefilledrectangle($img,$x1,$y1,$x2,$y2,$bar_color);
	}
	header("Content-type:image/png");
	imagepng($img);

?>

The above code is mostly right but there is some problem.like when the graph is being drawn the marks shown in the graph are not correct that means like if the student marks are 33 in the database then the graph shows the marks 40.it does not show the correct marks which are stored in the database...

Can you isolate the lines that are causing the problem?