This is a squared line plot, which is similar to a line plot but the points are connected with steps.
Example 5.13. Squared Plot

<?php
# PHPlot Example: squared plot
require_once 'phplot.php';
# To get repeatable results with 'random' data:
srand(1);
# Make some noisy data:
$data = array();
for ($i = 0; $i < 100; $i++)
  $data[] = array('', $i / 4.0 + 2.0 + rand(-20, 20) / 10.0);
$plot = new PHPlot(800, 600);
$plot->SetImageBorderType('plain');
$plot->SetPlotType('squared');
$plot->SetDataType('text-data');
$plot->SetDataValues($data);
$plot->SetTitle('Noisy Data (squared plot)');
# Make the lines a bit wider:
$plot->SetLineWidths(2);
# Turn on the X grid (Y grid is on by default):
$plot->SetDrawXGrid(True);
# Use exactly this data range:
$plot->SetPlotAreaWorld(0, 0, 100, 40);
$plot->DrawGraph();