title: How do I enable GMP on Mac OS X / PHP 7?
body: <p>I'm using PHP 7 and Mac High Sierra.  I'm trying to install and enable GMP.  I installed via</p>
  
  <pre><code>brew install homebrew/php/php70-gmp
  </code></pre>
  
  <p>but when I try and enable the module through the php.ini (/usr/local/etc/php/7.0/php.ini) file, I'm failing . I tried uncommenting the line</p>
  
  <pre><code>extension=php_gmp.dll
  </code></pre>
  
  <p>but I get this error when running composer</p>
  
  <pre><code>Warning: PHP Startup: Unable to load dynamic library '/usr/local/Cellar/php70/7.0.27_19/lib/php/extensions/no-debug-non-zts-20151012/php_gmp.dll' - dlopen(/usr/local/Cellar/php70/7.0.27_19/lib/php/extensions/no-debug-non-zts-20151012/php_gmp.dll, 9): image not found in Unknown on line 0
  </code></pre>
  
  <p>How do I enable GMP in my php.ini file?</p>