在php中为文件名生成随机字符串

function random_string($length) {
    $key = '';
    $keys = array_merge(range(0,9),range('a','z'));

    for ($i = 0; $i < $length; $i++) {
        $key .= $keys[array_rand($keys)];
    }

    return $key;
}

echo random_string(50);

输出示例：

zsd16xzv3jsytnp87tk7ygv73k8zmr0ekh6ly7mxaeyeh46oe8

编辑

在目录中使这个唯一,在这里更改为函数：

function random_filename($length,$directory = '',$extension = '')
{
    // default to this files directory if empty...
    $dir = !empty($directory) && is_dir($directory) ? $directory : dirname(__FILE__);

    do {
        $key = '';
        $keys = array_merge(range(0,'z'));

        for ($i = 0; $i < $length; $i++) {
            $key .= $keys[array_rand($keys)];
        }
    } while (file_exists($dir . '/' . $key . (!empty($extension) ? '.' . $extension : '')));

    return $key . (!empty($extension) ? '.' . $extension : '');
}

// Checks in the directory of where this file is located.
echo random_filename(50);

// Checks in a user-supplied directory...
echo random_filename(50,'/ServerRoot/mysite/myfiles');

// Checks in current directory of php file,with zip extension...
echo random_filename(50,'','zip');