title: i want to merge array having one unique value like id and other are different values and key also
body: <pre><code>    Array(
          [0] =&gt; Array(
              [billing_first_name] =&gt; pp
              [user_id] =&gt; 1
          )
          [1] =&gt; Array(
              [billing_last_name] =&gt; pp
              [user_id] =&gt; 1
          )
          [2] =&gt; Array(
              [billing_city] =&gt; Nagpur
              [user_id] =&gt; 1
          )
          [3] =&gt; Array(
              [billing_first_name] =&gt; gaurav
              [user_id] =&gt; 6
          )
          [4] =&gt; Array(
              [billing_last_name] =&gt; bokade
              [user_id] =&gt; 6
          )
      )
  </code></pre>
  
  <p>and I want Result As :</p>
  
  <pre><code>    Array(
          [0] =&gt; Array(
              [user_id] =&gt; 1
              [billing_first_name] =&gt; pp
              [billing_last_name] =&gt; pp
              [billing_city] =&gt; Nagpur
          )
          [1] =&gt; Array(
              [user_id] =&gt; 6
              [billing_first_name] =&gt; gaurav
              [billing_last_name] =&gt; bokade
              [billing_city] =&gt; 
          )
      )
  </code></pre>