Does that really work? I mean: "file created in the system's temporary directory" happens when tempnam returns false? Isn't the file created in the system's temporary directory returned instead?

Before the patch, in dev, I get the notice, and this notice is converted to an exception.
After the patch I get an exception with a proper error message.

So in both case I have to fix the permission.

Then, If I fix permissions, It works in both case.

Ok got it. Your are right. If I add the @ the result of the function is /tmp/classes.phpIo9eA9.
So the if false=== is useless.

What you I do? just add the @?

@lyrixx the goal of @ is to avoid the warning being triggered, so that our own exception is thrown rather than the ErrorException coming from the notice (allowing to have our more actionable error message)

and if (false === is not useless. It is the part detecting the error

I updated the code.

Oups, I forgot PHP 5.4.

I have different implementations:

        set_error_handler(function () use ($file) {
            throw new \RuntimeException(sprintf('Failed to create temporary file in "%s".', dirname($file)));
        });
        try {
            $tmpFile = tempnam(, basename($file));
        } catch(\RuntimeException $e) {
            restore_error_handler();

            throw $e;
        }
        restore_error_handler();

or something like

        $tmpFile = @tempnam(dirname($file), basename($file));
        if (dirname($file) !== dirname($tmpFile)) {
            throw new \RuntimeException(sprintf('Failed to write cache file "%s".', $file));
        }

or

        $dir = dirname($file);
        if (is_writable($dir)) {
            throw new \RuntimeException(sprintf('Failed to write cache in directory "%s".', $dir));
        }

Which one is the best?

Did the 3/

👍

Thank you @lyrixx.