will be read-only starting December 31st, 2018. For more info pleae look at this Forum Post

/* Simple test of the functionality of the photo resistor

Connect the photoresistor one leg to pin 0, and pin to +5V
Connect a resistor (around 10k is a good value, higher
values gives higher readings) from pin 0 to GND. (see appendix of arduino notebook page 37 for schematics).


           PhotoR     10K
 +5    o---/\/\/--.--/\/\/---o GND
 Pin 0 o-----------


int lightPin = 0;  //define a pin for Photo resistor
int ledPin=11;     //define a pin for LED

void setup()
    Serial.begin(9600);  //Begin serial communcation
    pinMode( ledPin, OUTPUT );

void loop()
    Serial.println(analogRead(lightPin)); //Write the value of the photoresistor to the serial monitor.
    analogWrite(ledPin, analogRead(lightPin)/4);  //send the value to the ledPin. Depending on value of resistor 
                                                //you have  to divide the value. for example, 
                                                //with a 10k resistor divide the value by 2, for 100k resistor divide by 4.
   delay(10); //short delay for faster response to light.