Remove duplicated values function
<pre><code>function remove_values($arr){
    $_a = array();
    while(list($key,$val) = each($arr)){
        $_a[$val] = 1;
    }
    return array_keys($_a);
}
</code></pre>

<p>i can't follow the above function well.i don't know what's the effect of  <code>$_a[$val] = 1;</code>  anyone can explain it to me thank you</p>
