gnuplot PNG from PHP

gistfile1.txt

$gnuplotcommands = '
set terminal png size 640x480
set grid
set autoscale
unset log
unset label
set xtics 0,1,23
set ytic auto
set title "Sample Chart Data"
set xlabel "Date"
set ylabel "Rainfall (in)"
set key left top
set boxwidth 0.75

$PLOTDATA << EOD
#Day Rainfall
1 0
2 2
3 4
4 3
5 0
6 0
EOD
plot $PLOTDATA using 2:xtic(1) with histogram fillstyle solid fillcolor "green" title "Rainfall", \
     $PLOTDATA using 0:($2 > 0 ? $2 : NaN):2 with labels notitle offset 0, char 1, \
';


	  $gnuplotcommandsArray = preg_split("/\r\n|\n|\r/", $gnuplotcommands);
		
		//openPipe()
        $descriptorspec = array(
            0 => array('pipe', 'r'),
            1 => array('pipe', 'w'),
            2 => array('pipe', 'r')
        );

        $process = proc_open('gnuplot', $descriptorspec, $pipes);

        if (!is_resource($process)) {
            throw new \Exception('Unable to run GnuPlot');
        }
		
		foreach ($gnuplotcommandsArray as $command) {
			fwrite($pipes[0], $command . PHP_EOL);
		}

        // Read data, timeout=100ms
        $result = '';
        $timeout = 100;
        do {
            stream_set_blocking($pipes[1], false);
            $data = fread($pipes[1], 128);
            $result .= $data;
            usleep(5000);
            $timeout-=5;
        } while ($timeout>0 || $data);
		

		header('Content-type: image/png');
		echo $result;		
		die();