title: Laravel validation: how mark as required an element of an item in array only if another is not present
body: <p>My api accept in post an array of recipients.</p>
  
  <p>Every recipients must have email OR phone, but NOT both.</p>
  
  <p>I tried this </p>
  
  <pre><code>'recipients'    =&gt; 'required|array|min:1',
      'recipients.*.email'     =&gt; 'required_without:recipients.*.phone',
      'recipients.*.phone'     =&gt; 'required_without:recipients.*.email',
  </code></pre>
  
  <p>The problem is that the following MUST BE discarded, but it is valid for laravel</p>
  
  <pre><code>{
    recipients: [
        'email': 'a'
        'phone: 'b'
    ]
  }
  </code></pre>
  
  <p>If there is email MUST NOT be the phone, and viceversa.</p>