Generate arbitrary string in php for file name

Question

How do I create a random string of text for use with file names?

I upload photos and rename them when done. All photos will be saved in one directory, so their names must be unique.

Is there a standard way to do this?

Is there a way to check if a file name exists before trying to overwrite?

It is for one user environment (s) to display my personal photos on my website, but I would like to automate it a bit. I don’t have to worry about two users trying to download and create the same file name at the same time, but I want to check if it already exists.

I know how to upload a file, and I know how to create random strings, but I want to know if there is a standard way to do this.

Answer 1

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); 

Output Example:

zsd16xzv3jsytnp87tk7ygv73k8zmr0ekh6ly7mxaeyeh46oe8

EDIT

Make it unique in the directory, change it here:

 function random_filename($length, $directory = '', $extension = '') { // default to this files directory if empty... $dir = !empty($directory) && is_dir($directory) ? $directory : dirname(__FILE__); do { $key = ''; $keys = array_merge(range(0, 9), range('a', 'z')); for ($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'); 

Answer 2

The right way to do this is to use the PHP tempnam() function. It creates a file in the specified directory with a guaranteed unique name, so you do not need to worry about randomness or overwrite an existing file:

 $filename = tempnam('/path/to/storage/directory', ''); unlink($filename); move_uploaded_file($_FILES['file']['tmp_name'], $filename); 

Answer 3

Hope this is what you are looking for: -

 <?php function generateFileName() { $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789_"; $name = ""; for($i=0; $i<12; $i++) $name.= $chars[rand(0,strlen($chars))]; return $name; } //get a random name of the file here $fileName = generateName(); //what we need to do is scan the directory for existence of the current filename $files = scandir(dirname(__FILE__).'/images');//assumed images are stored in images directory of the current directory $temp = $fileName.'.'.$_FILES['assumed']['type'];//add extension to randomly generated image name for($i = 0; $i<count($files); $i++) if($temp==$files[$i] && !is_dir($files[$i])) { $fileName .= "_1.".$_FILES['assumed']['type']; break; } unset($temp); unset($files); //now you can upload an image in the directory with a random unique file name as you required move_uploaded_file($_FILES['assumed']['tmp_name'],"images/".$fileName); unset($fileName); ?>