The package itself explained clearly how to do that. For example, to print it out-
echo DNS1D::getBarcodeSVG("4445645656", "PHARMA2T");
echo DNS1D::getBarcodeHTML("4445645656", "PHARMA2T");
echo '<img src="data:image/png,' . DNS1D::getBarcodePNG("4", "C39+") . '" alt="barcode" />';
echo DNS1D::getBarcodePNGPath("4445645656", "PHARMA2T");
echo '<img src="data:image/png;base64,' . DNS1D::getBarcodePNG("4", "C39+") . '" alt="barcode" />';
If you want to change width and height, here is the solution-
echo DNS1D::getBarcodeSVG("4445645656", "PHARMA2T",3,33);
echo DNS1D::getBarcodeHTML("4445645656", "PHARMA2T",3,33);
echo '<img src="' . DNS1D::getBarcodePNG("4", "C39+",3,33) . '" alt="barcode" />';
echo DNS1D::getBarcodePNGPath("4445645656", "PHARMA2T",3,33);
echo '<img src="data:image/png;base64,' . DNS1D::getBarcodePNG("4", "C39+",3,33) . '" alt="barcode" />';
Check more: https://github.com/milon/barcode