PHP GD Bar Chart

Jan 09, 2009 Author: Developer

Create Bar chart with PHP and GD

Its very easy i will show you in few steps

You must have installed GD and enable it

 

Firstly we are going to set a header type as image

PHP Code:
 header("Content-type: image/jpeg"); 

Now we are going to set some values in an array to use and then all them all together

PHP Code:

$data 
= array('3400','2570','245','473','1000','3456','780');
$sum array_sum($data); 

Now we need to set the height and width of the actual chart itself.

PHP Code:
$height 230;
$width 320

For the sake of this tutorial do not edit this. Otherwise this may cause errors.

Now we can create the actual chart background or where the chart is actually shown on. However you

want to look at it.

PHP Code:
$im imagecreate($width,$height); // width , height px 


Now we can set the background colour of the graph and also create some colours we are going to use for

the bars and the lines.

PHP Code:
$white imagecolorallocate($im,255,255,255); 
$black imagecolorallocate($im,0,0,0);   
$red imagecolorallocate($im,255,0,0); 

Now its time to create the X & Y axis lines.

PHP Code:

imageline
($im10510230$black );
imageline($im10230300230$black); 
PHP Code:
imageline  resource image,x-coordinate first point,y-coordinate first point,x-coordinate second point,y-coordinate second point,colour 

Now we need to set up some information so we can place these bars.

PHP Code:

$x 
15// set how far from the side then how far from next bar
$y 230// set where bar should reach on the y in this case on the y line we created
$x_width 20// Width of each of the bars 
$y_ht 0//height of the bars 

Now we can start creating the bars themself.

PHP Code:
for ($i=0;$i<7;$i++)
{
        
  
$y_ht = ($data[$i]/$sum)* $height// work out height and make sure they don't go larger then the image    

     
imagerectangle($im,$x,$y,$x+$x_width,($y-$y_ht),$red);
     
imagestring$im,2,$x-1,$y+10,$data[$i],$black);
              
  
$x += ($x_width+20); // set the new distance for the next bar 
         

Now we can display the final results

PHP Code:
imagejpeg($im); 

This bar chart can easily be upgraded.

Full Code

PHP Code:
<?php
  
           header
("Content-type: image/jpeg");
         
        
// read the post data
        
$data = array('3400','2570','245','473','1000','3456','780');
        
$sum array_sum($data);
        
        
$height 255;
        
$width 320;
        
        
$im imagecreate($width,$height); // width , height px

        
$white imagecolorallocate($im,255,255,255); 
        
$black imagecolorallocate($im,0,0,0);   
        
$red imagecolorallocate($im,255,0,0);   


        
imageline($im10510230$black);
        
imageline($im10230300230$black);
    

        
$x 15;   
        
$y 230;   
        
$x_width 20;  
        
$y_ht 0
       
        for (
$i=0;$i<7;$i++){
        
          
$y_ht = ($data[$i]/$sum)* $height;    
          
              
imagerectangle($im,$x,$y,$x+$x_width,($y-$y_ht),$red);
              
imagestring$im,2,$x-1,$y+10,$data[$i],$black);
              
          
$x += ($x_width+20);  
         
        }
        
        
imagejpeg($im);

?>

tags: php gd bar chart

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