updated code

#include<Servo.h>
const int pingPin = 7;
const int dangerThresh = 12;
const int PAN_MOTOR_PIN = 5;
const int DIR_DRIVE = 12; //DIRA
const int DIR_TURN = 13; //DIRB
const int BRAKE_DRIVE = 9; //BRAKEA
const int BRAKE_TURN = 8; //BRAKEB
const int PWM_DRIVE = 3; //PWMA
const int PWM_TURN = 11; //PWMB
int leftDistance, rightDistance;
Servo panMotor;
long duration;

void setup() {
  pinMode(DIR_DRIVE, OUTPUT);
  pinMode(DIR_TURN, OUTPUT);
  pinMode(BRAKE_DRIVE, OUTPUT);
  pinMode(BRAKE_TURN, OUTPUT);
  pinMode(PWM_DRIVE, OUTPUT);
  pinMode(PWM_TURN, OUPTUT);
  digitalWrite(BRAKE_DRIVE, LOW);
  digitalWrite(BRAKE_TURN, HIGH);
  digitalWrite(DIR_DRIVE, HIGH);
  analogWrite(PWM_DRIVE, 175);
  //panMotor.attach(11); // are you sure you want to use this pin for the servo?
  // why not 5 or 6? 11 is meant for the PWMB
  panMotor.attach(PAN_MOTOR_PIN);
  panMotor.write(90);
}

void loop() {
  int distanceFwd = ping();
  if(distanceFwd > dangerThresh) {
    digitalWrite(DIR_DRIVE, HIGH);
    digitalWrite(BRAKE_DRIVE, LOW);
    analogWrite(PWM_DRIVE, 175);
  } else {
    panMotor.write(0);
    delay(500);
    rightDistance = ping();
    delay(500);
    panMotor.write(160);
    delay(700);
    leftDistance = ping();
    delay(500);
    panMotor.write(90);
    delay(100);
    compareDistance();
  }
}

void compareDistance() {
  if(leftDistance > rightDistance) {
    digitalWrite(BRAKE_TURN, LOW);
    digitalWrite(DIR_TURN, HIGH);
    analogWrite(PWM_TURN, 255);
    delay(500);
  } else if(rightDistance > leftDistance) {
    digitalWrite(BRAKE_TURN, LOW);
    digitalWrite(DIR_TURN, LOW);
    analogWrite(PWM_TURN, 255);
    delay(500);
  } else {
    digitalWrite(DIR_DRIVE, HIGH);
    digitalWrite(BRAKE_DRIVE, LOW);
    analogWrite(PWM_DRIVE, 175);
  }
}

long ping() {
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);
  return duration / 29 / 2;
 }