Google Chart API in PHP

Google have released the Google Chart API which enables you to produce swizzy graphs like the above, which is the total 'hours-listened' to BBC Radio 1 from March 1999 to September 2007.

In their API documentation, they publish some JavaScript code to help with encoding the URL.

Here's the same thing in PHP - which, by default, will also sort out the maximum size as the maximum value in the array you pass it.

<?

// Here's an array containing some data to plot
$test_data=array(0.5,6,12,17,2,0.3,9);

// Here's where we call the chart, and return the encoded chart data
echo "<img src=http://chart.apis.google.com/chart?chtt=".urlencode("It's an example!")."&cht=lc&chs=450x125&chd=".chart_data($test_data).">";

// And here's the function

function chart_data($values) {

// Port of JavaScript from http://code.google.com/apis/chart/
// http://james.cridland.net/code

// First, find the maximum value from the values given

$maxValue = max($values);

// A list of encoding characters to help later, as per Google's example
$simpleEncoding = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';

$chartData = "s:";
  for ($i = 0; $i < count($values); $i++) {
    $currentValue = $values[$i];

    if ($currentValue > -1) {
    $chartData.=substr($simpleEncoding,61*($currentValue/$maxValue),1);
    }
      else {
      $chartData.='_';
      }
  }

// Return the chart data - and let the Y axis to show the maximum value
return $chartData."&chxt=y&chxl=0:|0|".$maxValue;
}

?>

Download this code

These are my personal views and not those of the BBC | Full disclosure | FAQ | Contact me | More Cridland stuff at www.cridland.net