Creating portal user through trigger

trigger CreatePortalUser on Contact (after insert, after update) {
    List usersToInsert = new List();
    List ExistingUsers = [Select contactId from User where contactId in: Trigger.NewMap.keySet()];
    Set contactsHavingUsers = new Set();
    for(User u : ExistingUsers) {
        contactsHavingUsers.add(u.Id);
    }
    Profile portalProfile = [select id, name from profile where name='Portal User'];  //Portal User is a custom profile already set up for your customer portal 
    String aliasVar = '';
    for(Contact con : Trigger.New) {
        if(!contactsHavingUsers.contains(con.Id) && con.Email != null) {
            if((con.LastName).length() > 8) {
                aliasVar = (con.LastName).substring(0, 8);  
            } else {
                aliasVar = con.LastName;
            }                
            User testUser = new User(alias = aliasVar, email = con.Email,
            emailencodingkey='UTF-8', lastname=con.LastName, languagelocalekey='en_US',
            localesidkey='en_US', profileid = portalProfile.Id, 
            timezonesidkey='America/Los_Angeles', username = con.Email, contactId=con.Id);                
            usersToInsert.add(testUser); 
        }
    }
    // Set the DML options
    Database.DMLOptions dlo = new Database.DMLOptions();
    dlo.EmailHeader.triggerUserEmail = true;         
    Database.insert(usersToInsert, dlo);    
}

Email and temporary password will be sent to user’s email id.