Are you using the output in a seperate file?
Or are you trying to put the output between the rest of your code?
Use it like
<img src="graph.php">
and then in graph.php put something like
<?php
header("Content-type: image/png");
//Include phpMyGraph5.0.php
include_once('phpMyGraph5.0.php');
//Set config directives
$cfg['title'] = 'Example graph';
$cfg['width'] = 500;
$cfg['height'] = 250;
//Set data
$data = array(
'Jan' => 12,
'Feb' => 25,
'Mar' => 0,
'Apr' => 7,
'May' => 80,
'Jun' => 67,
'Jul' => 45,
'Aug' => 66,
'Sep' => 23,
'Oct' => 23,
'Nov' => 78,
'Dec' => 23
);
//Create phpMyGraph instance
$graph = new phpMyGraph();
//Parse
$graph->parseHorizontalSimpleColumnGraph($data, $cfg);
?>