Although it is a advanced configuration it is common to share the connection to the network. You plug the PC into the phone and the phone into the wall that goes to the switch. In most cases you run the phone and the PC on a different vlan and the phone takes care of doing that. You can run them on the same vlan.
Most phones also have the ability to perfer its voice traffic over the PC traffic.
This design is common to save wiring and switch port costs.