title: what are session id? in php are session id assined to each user or each browser
body: <p>i am really confused about sessions in php i doing website this is my first project and i am stuck a user logging system i cant understand how php session work are these session id unique to each user or are these unique to each browser </p>
  
  <p>here is my problem</p>
  
  <p>when i login in using username and password for user1 i start a new session and a unique session id is created lets say phpssesid XXXXXXXXXXXXXXXX so when i logout from user1 i destroy session and session id XXXXXXXXXXXXXXXX generated during login for user1 is deleted from temp folder 
  next i login using user2 and password a new session  is again created but i get same session id i.e XXXXXXXXXXXXXXXX which was generated during first login i dont understand how come to users are assigned same session id to two different users</p>
  
  <p>all this while i was using google chrome to browse</p>
  
  <p>but then i used firefox to login using user1 and password but this time a new session id is created i.e XXXXXXXXXXXXXXX1 den i logout and again login using user2 and again session id assigned to user2 is same XXXXXXXXXXXXXXX1 </p>
  
  <p>i dont understand all this if sesssion id is unique to each user then why is same session id is assigned to two different users on same browser </p>