title: Laravel custom validation rule
body: <p>How can i make a custom validation rule to an input which value must be an integer and starting with 120? 
  I already read about making custom messages but didnt understand about rules.
  I want to use a regex to validate the data. <code>^120\d{11}$</code> here is my regex.
  I'm new in Laravel that's why cant now imagine how to do that.</p>
  
  <p>A custom validation to use it in <code>$this-&gt;validate($request, []);</code></p>
  
  <p>Now i'm validating data like so:</p>
  
  <pre><code>$this-&gt;validate($request, [
      'user_id' =&gt; 'integer|required',
      'buy_date' =&gt; 'date',
      'guarantee' =&gt; 'required|unique:client_devices|number',
      'sn_imei' =&gt; 'required|unique:client_devices',
      'type_id' =&gt; 'integer|required',
      'brand_id' =&gt; 'integer|required',
      'model' =&gt; 'required'
  ]);
  </code></pre>
  
  <p>The input that i want to add custom validation is <code>guarantee</code></p>