Using fopen() to write file into subdirectory

I already looked at this StackOverflow question and it didn't help (similarly titled). I'm passing an image in from my Android application. If I type ``` $file = fopen('test.jpg', 'wb'); ``` It works correctly and the image uploads; however, I want to allow for multiple uploads from android phones, so I want to randomize the name of the .jpg file so that I can save each new upload as a different name. I was trying this below: ``` $destination = time() + rand(1, 1000) . ".jpg"; $url_destination = "/project_images/" . $destination; $file = fopen($url_destination, 'wb'); fwrite($file, $binary); fclose($file); ``` It doesn't write the file to the server, however. I tried different variations of the URL there - with 'project_images/', '/project_images/', even trying the full URL (which the aforementioned StackOverflow post corrected me on), and I still can't get it to write. The permissions of the project_images folder are set to allow files to be written to it. Any ideas?