title: validation on exact length of numeric field in laravel 5
body: <p>I have numeric field i want to validate on exact fill 4 digits.</p>
  
  <p>like: 1234, 4567,1245</p>
  
  <p>but these invalid inputs:
  like: 123, 346, 45m6, 34567</p>
  
  <p>what I am trying:</p>
  
  <pre><code>'last4digits'             =&gt; 'numeric|between:4,4',
  </code></pre>