title: GCM/APNS How are registration IDs generated
body: <p>I am currently implementing a push notification server based on php that can manage multiple apps.</p>
  
  <p>How is the <strong>registration_id</strong> for GCM generated. Is the registration id generated per device or per installation.</p>
  
  <p>Example: I got 2 apps A and B.</p>
  
  <p>When the device registers for A and B, do the installations have the same registration ids or is one id generated per installation.</p>
  
  <p>The same question for iOS, one id per installation or device?</p>