title: how to access parameters from url in cakephp 3
body: <p>In cook book of cakephp 3. It is given to build url using</p>
  
  <pre><code>echo $this-&gt;Url-&gt;build([
      "controller" =&gt; "Posts",
      "action" =&gt; "view",
      "foo" =&gt; "bar"
  ]);
  </code></pre>
  
  <p>which will output as</p>
  
  <pre><code>/posts/view/foo:bar
  </code></pre>
  
  <p>How to access the <code>foo:bar</code> in action and save in a variable <code>$foo</code> ?</p>