Saving file to folder using file_put_contents() doesn't work

Question

I have been working on a little PHP script that dynamically creates & saves images in a folder tmp (which already exists!) from a base64 string. This is my save.php file.

// get base-64 string from form
$filteredData = substr($_POST['img_val'], strpos($_POST['img_val'], ",")+1);

// decode string
$unencodedData = base64_decode($filteredData);

// create unique filename
$a = uniqid();

// name, location and file extension
$compfile = '/tmp/' . $a . '.png';

// save image
file_put_contents($compfile, $unencodedData);

// print image
echo '<img src="' . $compfile . '" />';

Strangely enough: It will neither create nor render the image on the page, because of the /tmp/ in my $compfile variable. When I remove it, everything works like a charm and the image is being created in the same folder.

Unfortunately, I really want the image to be created in the /tmp/ folder. Before $compfile was a randomly generated filename, and instead was called /tmp/img.png I was able to save to create an image by the name img.png and save it to the tmp.

What am I missing here?

(Thank you for your time.)

Answer 1

Since I guess this was the solution I'll post it as answer.

I think you want "tmp/" . $a . ".png" instead of "/tmp/" . $a . ".png". It's good practice to just always use absolute paths, so: __DIR__ . "/tmp/" . $a . ".png". This takes away any confusion.