Is it possible to connect arduino uno to call a php script using ONLY an arduino uno board, and an esp8266-01 wifi module.? That is, I lack wifi shield such as node MCU. I just need the setup to call a php script on my localhost server. I'm using arduino IDE 1.8.13. Gracias
You can program the ESP-01 module using the arduino IDE. There are instructions in the README here: https://github.com/esp8266/Arduino
You can program the ESP-01 to connect to WiFi and communicate with your arduino sketch using the serial port. Don't forget the ESP-01 runs at 3.3V while the arduino runs at 5V. You'll need to shift the voltages somehow, otherwise you'll burn the arduino uno.
Here's an example of code you can run on the ESP-01 to connect to WiFi and start a TCP connection: https://github.com/esp8266/Arduino/blob/master/libraries/ESP8266WiFi/examples/WiFiClient/WiFiClient.ino
All that's missing is making an HTTP request instead of a "raw" TCP connection. You can probably find that in the examples. Then, add code for serial communication back to your arduino uno.