怎么从数组查找key对应的值

<br>$arr = [5=>&#39;name&#39;,8=>&#39;age&#39;,10=>&#39;city&#39;];
$num = &#39;5,10&#39;;
$str = &#39;&#39;;
//如何查找5,10对应的值，就是输出&#39;name,city&#39;,除了foreach还有什么更方便的办法?
foreach($arr as $key=>$value){
    if(strpos($num,$key) !== false) {
        $str.=$value;
    }
}

<?php
 
$arr = array(5=-->&#39;name&#39;,8=>&#39;age&#39;,10=>&#39;city&#39;);
$num = &#39;5,10&#39;;
 
$str = array();
$explode = explode(&#39;,&#39;,$num);
foreach($explode as $key){
    if(array_key_exists($key,$arr)){
        array_push($str,$arr[$key]);
    }
}
 
echo implode(&#39;,&#39;,$str);
 
?>