<?php
include_once '/usr/local/lib/openbabel.php';
$obMol = new OBMol();
$obMol->NewAtom();
$numAtoms = $obMol->NumAtoms();
# now 1 atom
$obMol->NewAtom();
$obMol->AddBond(1, 2, 1);
$numBonds = $obMol->NumBonds();
# now 1 bond
$obMol->Clear();
$obConversion = new OBConversion();
$obConversion->SetInAndOutFormats("smi", "svg");
$obConversion->ReadString($obMol, "C1=CC=CS1");
$numAtoms = $obMol->NumAtoms();
# now 5 atoms
$obMol->AddHydrogens();
$numAtoms = $obMol->NumAtoms();
# now 9 atoms
$outMDL = $obConversion->WriteString($obMol);
echo $outMDL;