Image taken from Wisconsin DOT live camera.
Data made up.
Note: This example requires PHPLOT version 4.4.1 or later.

<?
//Include the code
include( "../phplot.php");

//Define the object
$graph = new PHPlot(500,223, "", "0cars.jpg");
//$graph = new PHPlot(423,223);


//Set some data
$example_data = array(
    array( "55",5),
    array( "60",10),
    array( "65",20),
    array( "70",30),
    array( "75",25),
    array( "80",10));
$graph->SetDataValues($example_data);

//Set up some nice formatting things
$graph->SetTitle( "Speed Histogram");
$graph->SetXLabel( "Miles per Hour");
$graph->SetYLabel( "Percent of Cars");
$graph->SetVertTickIncrement(5);
$graph->SetPlotAreaWorld(0,0,6,35);

//Make the margins nice for the background image
$graph->SetMarginsPixels(80,35,35,70);

//Set up some color and printing options
$graph->background_done = 1;   //The image background we get from 0cars.jpg
$graph->SetDrawPlotAreaBackground(0);  //Plot Area background we get from the image
$graph->SetDataColors(array( "white"),array( "black"));

//Set Output format
$graph->SetFileFormat( "png");

//Draw it
$graph->DrawGraph();

?>