function change()
{
$pdf_file = './pdf/demo.pdf';
$save_to = './jpg/demo.jpg'; //make sure that apache has permissions to write in this folder! (common problem)//execute ImageMagick command 'convert' and convert PDF to JPG with applied settings
exec('convert "' . $pdf_file . '" -colorspace RGB -resize 800 "' . $save_to . '"', $output, $return_var);
if ($return_var == 0) { //if exec successfuly converted pdf to jpg
print "Conversion OK";
} else{
print "Conversion failed.<br />" . $output;
}
}