title: Add to array only if there isn't a key with the same value?
body: <p>I want to add <code>$variable</code> only if there isn't a key with the same value in array <code>$insertar["Atributos"]</code>.</p>
  
  <pre><code>$insertar["Atributos"][] = $variable;
  </code></pre>
  
  <p>I can do it using a foreach to check beforehand if <code>$variable</code> is stored and insert only if it isn't but I want to know if there is an easier way.</p>