Callback function not executing second statement - C++ MQTT - c++

Question

I've programmed a callback function that handles MQTT messages (payload). I want to switch of pins not based on an incoming payload. The problem I have now is that the first statement is executed nicely when sending 11. However the second statement is not working. Strangely when I send two messages one containing 1x and the other x1 I can again toggle both pins. It's a very strange problem!
Could anyone help me with this, thanks very much. I'm using the PubSubClient library.
void callback(char* topic, byte* payload, unsigned int length) {
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("] ");
for (int i = 0; i < length; i++) {
Serial.print((char)payload[i]);
}
//Set GPIO0 to HIGH or LOW on first character received in message
if (payload[0] == '1') {
digitalWrite(GPIO0, HIGH); // Turn the relay on
client.publish(getOutTopic().c_str(), "GPIO0 set to HIGH");
} else if (payload[0] == '0') {
digitalWrite(GPIO0, LOW); // Turn the relay off
client.publish(getOutTopic().c_str(), "GPIO0 set to LOW");
}
//Set GPIO2 to HIGH or LOW on first character received in message
if (payload[1] == '1') {
digitalWrite(GPIO2, HIGH); // turn LED off. With High it is inactive on the ESP-01)
client.publish(getOutTopic().c_str(), "GPIO2 set to HIGH");
} else if (payload[1] == '0') {
digitalWrite(GPIO2, LOW); // Turn the LED on by making the voltage LOW
client.publish(getOutTopic().c_str(), "GPIO2 set to LOW");
}
}

Answer 1

The client.publish destroys the payload buffer. So I had to catch the payloads into new variables to overcome the problem.
void callback(char* topic, byte* payload, unsigned int length) {
char p0 = (char)payload[0];
char p1 = (char)payload[1];
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("] ");
for (int i = 0; i < length; i++) {
Serial.print((char)payload[i]);
}
//Set GPIO0 to HIGH or LOW on first character received in message
if (p0 == '1') {
digitalWrite(GPIO0, HIGH); // Turn the relay on
client.publish(getOutTopic().c_str(), "GPIO0 set to HIGH");
} else if (p0 == '0') {
digitalWrite(GPIO0, LOW); // Turn the relay off
client.publish(getOutTopic().c_str(), "GPIO0 set to LOW");
}
//Set GPIO2 to HIGH or LOW on first character received in message
if (p1 == '1') {
digitalWrite(GPIO2, HIGH); // turn LED off. With High it is inactive on the ESP-01)
client.publish(getOutTopic().c_str(), "GPIO2 set to HIGH");
} else if (p1 == '0') {
digitalWrite(GPIO2, LOW); // Turn the LED on by making the voltage LOW
client.publish(getOutTopic().c_str(), "GPIO2 set to LOW");
}
}