title: Generating unique non-random id based on CSV row?
body: <p>I have a CSV in the format:</p>
  
  <pre class="lang-none prettyprint-override"><code>Bill,Smith,123 Main Street,Smalltown,NY,5551234567
  Jane,Smith,123 Main Street,Smalltown,NY,5551234567
  John,Doe,85 Main Street,Smalltown,NY,5558901234
  John,Doe,100 Foo Street,Bigtown,CA,5556789012
  </code></pre>
  
  <p>In other words, no one field is unique.  Two people can have the same name, two people can have the same phone, etc., but each line is itself unique when you consider all of the fields.</p>
  
  <p>I need to generate a unique ID for each row but it cannot be random.  And I need to be able to take a line of the CSV at some time in the future and figure out what the unique ID was for that person without having to query a database.</p>
  
  <p>What would be the fastest way of doing this in PHP?  I need to do this for millions of rows, so <code>md5()</code>'ing the whole string for each row isn't really practical.  Is there a better function I should use?</p>