I'm designing a web site for a travel company, and they would like to add an online payment system that takes credit cards. I am open to suggestions on what's available, keeping in mind these requirements:
- must be written in PHP
- reasonable price (I assume there's no freeware option, is there?)
- secure & reliable performance, I won't recommend something to them just because it's affordable
- can handle credit card transactions
- one-time license payment to use it, I don't want them to have to deal with yearly subscriptions or other such complications
- mature software, something that's unlikely to need upgrades in the near future
I respectfully thank you in advance for any input!