怎么用php写一个日志功能的函数

<code><span>log</span>(){
    <span>$args</span> = func_get_args();<span>//获得传入的所有参数的数组</span><span>$numargs</span> = func_num_args(); <span>//参数的个数</span><span>if</span> (<span>$numargs</span> == <span>0</span>) {
        <span>$log</span> = <span>""</span>;
    } elseif (<span>$numargs</span> == <span>1</span>) {
        <span>$log</span> = <span>$args</span>[<span>0</span>];
    } <span>else</span> {
        <span>$format</span> = array_shift(<span>$args</span>); <span>//分割掉函数第一个元素,并且做返回值返回,'$user_address:%s'</span><span>$log</span> = vsprintf(<span>$format</span>, <span>$args</span>); <span>//把参数代入$format中,</span>
    }
    <span>$log</span> = <span>date</span>(<span>"[Y/m/d H:i:s] "</span>) . <span>$log</span> . PHP_EOL;<span>//加上时间</span><span>$file</span> = <span>'/usr/share/nginx/html/log.log'</span>;
    <span>$fp</span> = <span>fopen</span>(<span>$file</span>, <span>'a'</span>);
    <span>fwrite</span>(<span>$fp</span>, <span>$log</span>);
    <span>fclose</span>(<span>$fp</span>);
    <span>return</span> true;
    } 
</code>