Simple bar graph using GD and PHP

This is a simple piece of code to display a bar chart in PHP using GD.

Store the values you wish to chart in an array. The code will size the columns to fit the width and height specified for the graph. The value in $padding is used to provide a space between each column.

The code in the example returns the graph in PNG format. You can obviously change this to any other format you wish. Just remember that when using JPEG you will experience some loss of sharpness in the image, and it may not be suitable for this type of image application.

<?php

        

        // This array of values is just here for the example.

        

    $values = array("23","32","35","57","12",

                    "3","36","54","32","15",

                    "43","24","30");

      

      // Get the total number of columns we are going to plot

      

    $columns  = count($values);

      

      // Get the height and width of the final image

      

    $width = 300;

    $height = 200;

      

      // Set the amount of space between each column

      

    $padding = 5;

      

      // Get the width of 1 column

      

    $column_width = $width / $columns ;

      

      // Generate the image variables

      

    $im        = imagecreate($width,$height);

    $gray      = imagecolorallocate ($im,0xcc,0xcc,0xcc);

    $gray_lite = imagecolorallocate ($im,0xee,0xee,0xee);

    $gray_dark = imagecolorallocate ($im,0x7f,0x7f,0x7f);

    $white     = imagecolorallocate ($im,0xff,0xff,0xff);

    

// Fill in the background of the image

      

    imagefilledrectangle($im,0,0,$width,$height,$white);

    

    $maxv = 0;

      

      // Calculate the maximum value we are going to plot

      

    for($i=0;$i<$columns;$i++)$maxv = max($values[$i],$maxv);

      

      // Now plot each column

        

    for($i=0;$i<$columns;$i++)

    {

        $column_height = ($height / 100) * (( $values[$i] / $maxv) *100);

      

        $x1 = $i*$column_width;

        $y1 = $height-$column_height;

        $x2 = (($i+1)*$column_width)-$padding;

        $y2 = $height;

      

        imagefilledrectangle($im,$x1,$y1,$x2,$y2,$gray);

      

      // This part is just for 3D effect

      

        imageline($im,$x1,$y1,$x1,$y2,$gray_lite);

        imageline($im,$x1,$y2,$x2,$y2,$gray_lite);

        imageline($im,$x2,$y1,$x2,$y2,$gray_dark);

      

    }

      

      // Send the PNG header information. Replace for JPEG or GIF or whatever

      

    header ("Content-type: image/png");

    imagepng($im);

?>