title: Change website to .php from .html , will this hurt my seo rankings
body: <p>Quick question.</p>
  
  <p>I have a client with an HTML based website which ranks very, very high for SEO and has been around for 8 years.</p>
  
  <p>I want to revamp his site using php templates and implement some CMS.</p>
  
  <p>Will my re-writing the pages from .html to .php hurt his ranking in any way?</p>
  
  <p>Thanks in advance!</p>