title: laravel validation Array to string conversion error
body: <p>if I check min|max before exist 
  laravel validation will return Array to string conversion error.
  (laravel version 5.5)</p>
  
  <pre class="lang-php prettyprint-override"><code>return [
      // 'nick_name' =&gt; 'exists:users|max:150|min:6|regex:/\A[0-9a-zA-Z_]{6,150}\z/',
      'nick_name' =&gt; ['max:150', 'min:6', 'exists:users', 'regex:/\A[0-9a-zA-Z_]{6,150}\z/'],//return Array to string conversion error
      // 'nick_name' =&gt; ['exists:users', 'max:150', 'min:6', 'regex:/\A[0-9a-zA-Z_]{6,150}\z/'],//success
      'ref_code' =&gt; 'exists:users',
  ]
  </code></pre>