title: create a email checker using php codeigniter
body: <p>Please help me in creating a form which allows a user to submit valid email.</p>
  
  <p>When someone try to enter an email id, it should be validated before submitted to data base. Some of the  examples for junk email ids are <code>test@abc.com</code>, <code>123@xyz.com</code> etc.</p>
  
  <p>If an user try to enter an email id as mentioned in the above example, it should be verified whether it is a valid email id or not and also check if the user with the email id already exists?</p>
  
  <p>Kindly help me building a code in php codeigniter.</p>