php从文件夹随机读取文件的方法

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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