an><span class="phpdocumentor-signature__argument__name">$keys</span></span><span class="phpdocumentor-signature__argument"><span>[</span><span>, </span><span class="phpdocumentor-signature__argument__return-type">mixed&nbsp;</span><span class="phpdocumentor-signature__argument__name">$default</span><span> = </span><span class="phpdocumentor-signature__argument__default-value">null</span><span> ]</span></span><span>)</span><span> : </span><span class="phpdocumentor-signature__response_type">iterable&lt;stri