PHP create real-time
dynamic chart
Many web sites need to create real-time or dynamic charts and graphs(like
online stocks, web traffic statistics) from live data sets. PHP and
GD library provides a great way for this dynamic creation of images.
PHP and GD library creates image on server side. The advantage
of using the server to create an image (server side scripting) is
that one does not have to worry about browser compatibility or client
operating system compatibility issues.The PHP image generating
library uses the GD library to create elementary shapes (elipse,
line, rectangle, ...).
PHPlot is a graphics library which provides
a means by which you can have your (PHP enabled) web server create
and manipulate graphs as objects and display the completed graph
as an image. Data sets passed to PHPlot use a very convenient
way for database driven sites, in rows with y coordinate data.
First, lets discuss how PHPlot works in general with some terminology.
A PHPlot image can consist of several graphs , each
graph consisting of several elements. You define an object
(e.g. a variable like $graph), select the properties
of the element that compose the graph and "Draw" what you
want into the object. Tipically by selecting the plot type with SetPlotType and
at the end calling DrawGraph. You can also directly
invoke PrintImage, which either inserts the image into
the data streaming to the client or writes it to disk.
In PHPlot there are World coordinates, which are the XY
coordinates relative to the axis origin, in the units of the data
set; and device (pixel) coordinates which in GD are relative
to the origin at the upper left side of the image.
You can think of the "Draw" functions as shaping the image object
and the "Print" function as the method of finally creating the digital
image. PHPlot is smart enough that if you only have one graph on
an image, then the "Print" is done for you automatically. If you
do have multiple graphs per image then you'll need to use both the "Draw" and "Print" functions.
We'll talk about that a bit later.
Since PHP is a server scripted language you have several options
for how you can "Print" the image. You can:
- Write the image as a file on the server. (You specify a file
name and can specify caching as well)
- Have the raw data stream out within an HTML file, as <IMG
SRC="my_PHPlot_code.php">
- Precede the raw data with html image headers and call the script
directly (showing up as an image) e.g. http://somewhere/my_PHPlot_code2.php
.
Download PHPlot
PHPlot 5.0RC2 is available
here .
Unzip file
UNIX:
tar zxvf phplot-5.0rc2.tar.gz
Windows: using your favorite unzip software.Move to your web direstory.
System Requirement
PHP 4.2.0 (or later) and GD Lib 2 are necessary. Works
good for Windows and Linux(at least).
You may test your system ready or not by using this example.
Real-time dynamic chart examples
A simple graph
 |
<?php
//Include the code
include("phplot/phplot.php");
//Define the object
$graph =& new PHPlot(200,150);
//Define some data
$example_data = array(
array('a',3),
array('b',5),
array('c',7),
array('d',8),
array('e',2),
array('f',6),
array('g',7)
);
$graph->SetDataValues($example_data);
$graph->SetXTickPos('none');
$graph->SetXTickLabelPos('none');
//Draw it
$graph->DrawGraph();
?> |
Multiple line graph
Assume we want to plot several
y values for each x position. With PHPlot it is easy to specify the
multiple data lines by just passing in all the Y values for a given
X value at once. So instead of array('label', y) we specify array('label',
y1, y2, y3, ...) This is very convenient
when working with rows of data from databases.
Now our data will have three Y values for each position on the X axis
 |
<?php
//Include the code
include("phplot/phplot.php");
//Define the object
$graph =& new PHPlot(300,250);
//Set titles
$graph->SetTitle("Title\n\rSubtitle");
$graph->SetXTitle('X data');
$graph->SetYTitle('Y data');
//Define some data
$example_data = array(
array('a',3,4,2),
// here we have a missing data point, that's ok
array('b',5,'',1),
array('c',7,2,6),
array('d',8,1,4),
array('e',2,4,6),
array('f',6,4,5),
array('g',7,2,3)
);
$graph->SetDataValues($example_data);
$graph->SetXTickPos('none');
$graph->SetXTickLabelPos('none');
//Draw it
$graph->DrawGraph();
?>
|
See the above data, PHPlot could allow missing data.
$graph = &new PHPlot(); create an PHPlot instance. The
image default size is 600 X 400 png. You may set to GIF JPG (depend
on your system supprort) by changing
var $file_format = "<filetype>";
in phplot.php file. such as var
$file_format = "GIF";
Pie chart
 |
<?php
//Include the code
include('phplot/phplot.php');
//Define the object
$graph =& new PHPlot(200,150);
$graph->SetPlotType("pie");
$legend = array();
$legend[] = "stock 1";
$legend[] = "stock 2";
$legend[] = "stock 3";
//Define some data
$example_data = array(
array('a',3,4,5)
);
$graph->SetDataValues($example_data);
$graph->SetLegendPixels(1,5,false);
$graph->SetLegend($legend);
//Draw it
$graph->DrawGraph();
?>
|
For pie chart, you must define plot type before drawing
by SetPlotType("pie");.
Also note that, if you use the following data format:
$example_data = array(
array('a',3),
array('b',5),
array('c',7),
array('d',8),
array('e',2),
array('f',6)
);
shown
in above code for pie chart, you need define $graph->SetDataType("text-data-single"); . Or if you use data format like $example_data=array(array('piechart',5,6,7,8)
you may omit $graph->SetDataType("text-data-single");
|
