title: how to run lower PHP version code (codeigniter) into higher php version
body: <p>I am using CodeIgniter version 3.1.6. And I am using two types of PHP version codeings.</p>
  
  <p>First one is PHP 5.6.35 and another one is 7.1.16. I use PHP 7.1.16 to use Apache Solr.</p>
  
  <p>But the PHP 5.6.35 version support coding is not working if PHP version is 7.1.16. And the PHP 7.1.16 coding is not working in PHP 5.6.35.</p>
  
  <p>I can't change CodeIgniter version, because totally 80% work depend on lower version. At the same time I need PHP higher version codeings also.</p>
  
  <p>Now my question is if it is possible to run lower PHP version code into higher PHP version.</p>