title: Change mac os x default php version
body: <p>In my mac (<strong>version 10.13.6 High Sierra</strong>) <code>php -v</code> output is <code>PHP 7.1.32</code> . 
  I need to update this 7.1 version to 7.3.</p>
  
  <p>i tried to remove this version using <code>brew unlink php7.1</code> but it's not worked.</p>
  
  <p>How can i upgrade php version.</p>