Understanding _ids array in CakePHP model data : <p>Using CakePHP v3.1 w/ Postgres DB. When I retrieve records with associations I often see an extra array of <code>_ids</code>. Something like this:</p>

<pre><code>    ...
    (int) 26 =&gt; [
        'agency_id' =&gt; (int) 23,
        'routes' =&gt; [
            '_ids' =&gt; (int) 2
        ]
    ]
</code></pre>

<p>Or sometimes:</p>

<pre><code>     '_ids' =&gt; Array (
        0 =&gt; 1
        1 =&gt; 5
        2 =&gt; 3
        3 =&gt; 4
     )
]
</code></pre>

<p>I would like to understand:</p>

<ol>
<li>How and why do these magic <code>_ids</code> appear?</li>
<li>Is there a way to control or prevent that behavior?</li>
</ol>
