php實現linux tail -n 命令

<?
/**
* 读取文本倒数$n行
*
* @param string $filename
* @param int $n $n不能大于10
* @return array
*/
header("Content-type: text/html;charset=gb2312");
$filename = "log/log.txt";
$fileData = tail($filename,100);
for($i=0;$i<count($fileData);$i++)
{
echo $fileData[$i]."<br>";
}
function tail($filename,$n)
{
        $fp = fopen($filename, 'rb');
        $n = (int)$n;
        if($n>10) trigger_error("取文件倒数N行的时候,不能大于10行", E_USER_ERROR);
        if ($fp) {
                flock($fp, LOCK_SH);
                $i = -2;//从第二个字符开始,因为最后一个是"\n"
                fseek($fp,$i,SEEK_END);
                $buffer = array();
                while ($n>=0) {
                 fseek($fp,$i--,SEEK_END);
     if(fgetc($fp)=="\n") {
        $buffer[] = fgets($fp,1024);
        $n--;
     }
                }
                flock($fp, LOCK_UN);
                fclose($fp);
                unset($tmp);
                return $buffer;
        } else {
                return false;
        }
}
?>