In the Arduino ESP8266 Web Server library, you can use the header method to get the value of a specific header. Here’s an example of how you can do this:

server.on("/getValues", HTTP_POST, []() {
    if(server.hasHeader("MyHeader")) {
        String headerValue = server.header("MyHeader");
        // Use headerValue...
    server.send(200, "text/plain", "OK");

In this example, server.hasHeader("MyHeader") checks if the request contains a header named “MyHeader”. If it does, server.header("MyHeader") gets the value of the “MyHeader” header. Replace “MyHeader” with the name of the header you want to read.