Connect Arduino UNO to API

Hi, Guys i need a idea, i have a Arduino UNO and i want that it communicate with my API, but i don't have ethernet shield, can i use serial port to do this communication? and communication API return some value, to the arduino.

Thanks.

and i want that it communicate with my API

API = Application Programming Interface. Where, exactly, is this application running?

can i use serial port to do this communication?

Does the application listen to the serial port?

i want to create a http connect on my Arduino to send an information to my web service, and returns some information, likes true or false, all this using Serial PHP.

i want to create a http connect on my Arduino to send an information to my web service, and returns some information, likes true or false, all this using Serial PHP.

No, this is NOT what you want to do. If it was, you'd get an ethernet shield.

Thanks for your answer,

I need to do a Access Control, i have one Arduino UNO and RFID shield, how can i do to my arduino communicate with my php server to save the date and TAG entry to the system.

Thanks again.