Most passport holders can get a visa on arrival.
Passport holders from Afghanistan, Bangaladesh, Iran, Nigeria, Yemen and Sudan need to have a visa organised prior to arrival.
Passport holders from Angola, Albania, Belize, Benin, Botswana, Burkina Faso, Burundi, Cambodia, Central Africa, Chad , Congo, Colombia, Cameroon, Côte d’Ivoire, Cuba, Djibouti, Eritrea, Ethiopia, Equatorial Guinea, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Iraq, Laos, Liberia, Libya, Madagascar, Mali, Mauritania, Moldova, Mongolia, Mozambique, Myanmar, Namibia, Nepal, Niger, Pakistan, Papua New Guinea, Philippine, Senegal, Sierra Leone, Somalia, South Sudan, Srilanka, Tanzania, Togo, Uganda, Union of the Comoros, Vietnam, Zaire and Zambia need a visa but if they have a resident permit from European Union, GCC, United Kingdom or USA they can get a visa on arrival.
Visa on arrival costs around US$60.
If you leave Jordan at the Allenby/King Hussein bridge crossing with Israel, then return while the visa is still valid you do not need to buy a new one. This is because West Bank is recognized by Jordan as a part of Jordan. If you enter Jordan a the Allenby/King Hussein Bridge you will not be able to get a visa on arrival.
If you are entering through Aqaba you do not need to pay for the visa.
Jordan visa information
Jordan embassies worldwide