请教个问题.以下是一个PHP文件全部代码

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function RandomFile($folder='', $extensions='.*'){

// fix path:

$folder = trim($folder);

$folder = ($folder == '') ? './' : $folder;

// check folder:

if (!is_dir($folder)){ die('invalid folder given!'); }

// create files array

$files = array();

// open directory

if ($dir = @opendir($folder)){

// go trough all files:

while($file = readdir($dir)){

if (!preg_match('/^\.+$/', $file) and

preg_match('/\.('.$extensions.')$/', $file)){

// feed the array:

$files[] = $file;

}

}

// close directory

closedir($dir);

}

else {

die('Could not open the folder "'.$folder.'"');

}

if (count($files) == 0){

die('No files where found :-(');

}

// seed random function:

mt_srand((double)microtime()*1000000);

// get an random index:

$rand = mt_rand(0, count($files)-1);

// check again:

if (!isset($files[$rand])){

die('Array index was not found! very strange!');

}

// return the random file:

return $folder . $files[$rand];

}

//用法演示：

// "jpg|png|gif" matches all files with these extensions

//print RandomFile('test_images/','jpg|png|gif');

// returns test_07.gif

// ".*" matches all extensions (all files)

//print RandomFile('test_files/','.*');

// returns foobar_1.zip

// "[0-9]+" matches all extensions that just

// contain numbers (like backup.1, backup.2)

//print RandomFile('test_files/','[0-9]+');

// returns backup.7

//随机从file.txt文本文件中读取一行出来

$file = RandomFile('so/data/sitemap/','.*'); //文件位置;

//是否存在

if(file_exists($file)){

$data = file($file); //将文件存放在一个数组中;

$num = count($data); //条数;

$id = mt_rand(0,$num-1); //随机数字;

$cn_text = chop($data[$id]); //显示第几行数据,并去除空格;

}

function characet($cn_text){

if( !empty($cn_text) ){

$fileType = mb_detect_encoding($cn_text , array('UTF-8','GBK','LATIN1','BIG5')) ;

if( $fileType != 'UTF-8'){

$data = mb_convert_encoding($cn_text ,'utf-8' , $fileType);

}

}

return $cn_text;

}

//header ('Content-Type:text/html;charset=utf-8');

//echo ($cn_text);

//echo 'document.write(“‘. $cn_text .'”);’;

//echo “document.getElementById(‘”.$keywords.”‘).innerHTML='”.$cn_text.”‘;”;

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请问在html文件中如何调用这个文件随机从txt当中读取的字符串?