Graphing with PHP and GD Page 5

What we need to do is alter our code that determines the y position so that it works in the opposite way – change the line.

<?php
    ImageLine($image,$points[$i][0],$points[$i][1],$points[$i+1][0],$points[$i+1][1],$red);
?>

To read:

<?php
ImageLine($image,$points[$i][0],200-$points[$i][1],$points[$i+1][0],200-$points[$i+1][1],$red);
?>

And we are presented with the graph:

All we need to do now is add a line that graphs the data from Atlanta and we’ll be done.

<?php
  $sql = "SELECT g_num FROM sales WHERE g_team='Atlanta' ORDER BY g_month";
  $salesResult = mysql_query($sql,$connect);
  $columns = mysql_num_rows($salesResult);
  $xincrement = bcdiv(200,$columns-1,0);
  $x=0;
  $i=0;
  while($salesRow=mysql_fetch_array($salesResult)) {
      $y = bcmul(bcdiv($salesRow[0],$max,2),200,2);
    $points[$i][0] = $x;
    $points[$i][1] = $y;
    $x+=$xincrement;
    $i++;
  }
  for($i=0;$i<$columns-1;$i++) {
    ImageLine($image,$points[$i][0],200-$points[$i][1],$points[$i+1][0],200-$points[$i+1][1],$blue);
  }
?>

The data we’ve used in this example has been static – in the next section we’ll take
a look at how we can handle dynamic data and have a look at adding some axes and labels to the graph.

–Allan