title: split string of emails into groups if string is longer than 50 emails
body: <p>Is there an efficient way to split a string containing a list of email addresses into groups of say 50?  Say I have a string that contains emails in a comma-separated format.  Something like...  email1@host.com,email2@host.com,email3@host.com and so on.</p>
  <p>The most obvious way to do this would probably be an array, but is there a way to do it with string functions?  I have looked at substr and str_split and they don't quite seem to do the job.</p>