unsigned long ping() {
pinMode(pingPin, OUTPUT); // Make the Pingpin to output
digitalWrite(pingPin, LOW); //Send a low pulse
delayMicroseconds(2); // wait for two microseconds
digitalWrite(pingPin, HIGH); // Send a high pulse
delayMicroseconds(5); // wait for 5 micro seconds
digitalWrite(pingPin, LOW); // send a low pulse
pinMode(pingPin,INPUT); // switch the Pingpin to input
duration = pulseIn(pingPin, HIGH); //listen for echo
unsigned long ping(); <<<<HERE
pinMode(TrigPin, OUTPUT); // Make the Pingpin to output
digitalWrite(TrigPin, LOW); //Send a low pulse
delayMicroseconds(2); // wait for two microseconds
digitalWrite(TrigPin, HIGH); // Send a high pulse
delayMicroseconds(5); // wait for 5 micro seconds
digitalWrite(TrigPin, LOW); // send a low pulse
pinMode(EchoPin,INPUT); // switch the Pingpin to input
duration = pulseIn(EchoPin, HIGH); //listen for echo
that's an unusual place to put a function prototype.
Difficult (for me) to see what you're trying to achieve.
If you've got two sensors, on different pins, make a single function with the pin number as parameter.