PHP Fastest way to check if a value in the array exists
<p>I have this array:</p>

<pre><code>array [▼
      0 =&gt; array:5 [▼
        "id" =&gt; 1
        "user_id" =&gt; 15
        "parent_campaign_id" =&gt; 69464
        "child_campaign_id" =&gt; 69464
        "cpm" =&gt; "1.00"
      ]
      1 =&gt; array:5 [▼
        "id" =&gt; 2
        "user_id" =&gt; 15
        "parent_campaign_id" =&gt; 69464
        "child_campaign_id" =&gt; 396331
        "cpm" =&gt; "2.00"
      ]
      2 =&gt; array:5 [▼
        "id" =&gt; 3
        "user_id" =&gt; 15
        "parent_campaign_id" =&gt; 69464
        "child_campaign_id" =&gt; 398032
        "cpm" =&gt; "3.00"
      ]
    ]
</code></pre>

<p>How can I know if a number <code>396331</code> exists in that array and the key should be <code>child_campaign_id</code>.</p>

<p>I tried <code>in_array()</code> but it seems it is not working correctly since the <code>keys</code> of this array is different.</p>

<p>Your help will be greatly appreciated.</p>