cordova - upload images through php using unique file names

Question

I am currently in the process of writing a mobile app with the help of phonegap. One of the few features that I would like this app to have is the ability to capture an image and upload it to a remote server...

I currently have the image capturing and uploading/emailing portion working fine with a compiled apk... but in my php, I am currently naming the images "image[insert random number from 10 to 20]... The problem here is that the numbers can be repeated and the images can be overwritten... I have read and thought about just using rand() and selecting a random number from 0 to getrandmax(), but i feel that I might have the same chance of a file overwriting... I need the image to be uploaded to the server with a unique name every-time, no matter what... so the php script would check to see what the server already has and write/upload the image with a unique name...

any ideas other than "rand()"?

I was also thinking about maybe naming each image... img + date + time + random 5 characters, which would include letters and numbers... so if an image were taken using the app at 4:37 am on March 20, 2013, the image would be named something like "img_03-20-13_4-37am_e4r29.jpg" when uploaded to the server... I think that might work... (unless theres a better way) but i am fairly new to php and wouldn't understand how to write something like that...

my php is as follows...

print_r($_FILES);
$new_image_name = "image".rand(10, 20).".jpg";
move_uploaded_file($_FILES["file"]["tmp_name"], "/home/virtual/domain.com/public_html/upload/".$new_image_name);

Any help is appreciated... Thanks in advance! Also, Please let me know if there is any further info I may be leaving out...

Answer 1

You may want to consider the PHP's uniqid() function. This way the code you suggested would look like the following:

$new_image_name = 'image_' . date('Y-m-d-H-i-s') . '_' . uniqid() . '.jpg';
// do some checks to make sure the file you have is an image and if you can trust it
move_uploaded_file($_FILES["file"]["tmp_name"], "/home/virtual/domain.com/public_html/upload/".$new_image_name);

Also keep in mind that your server's random functions are not really random. Try random.org if you need something indeed random. Random random random.

UPD: In order to use random.org from within your code, you'll have to do some API requests to their servers. The documentation on that is available here: www.random.org/clients/http/.

The example of the call would be: random.org/integers/?num=1&min=1&max=1000000000&col=1&base=10&format=plain&rnd=new. Note that you can change the min, max and the other parameters, as described in the documentation.

In PHP you can do a GET request to a remote server using the file_get_contents() function, the cURL library, or even sockets. If you're using a shared hosting, the outgoing connections should be available and enabled for your account.

$random_int = file_get_contents('http://www.random.org/integers/?num=1&min=1&max=1000000000&col=1&base=10&format=plain&rnd=new');
var_dump($random_int);