Why does my server keep creating new files with 0640 permissions in my PHP fwrite?

Question

I'm using a simple fopen("w") and fwrite setup to write a new file on my server. Recently, this has been arbitrarily assigning 0640 permissions to these files, which means I can't view them from a browser. But it's not happening every time. Can anybody tell me why? What I'm missing here? Here's my code:

if ($file=fopen("$filesDir/$yr/$mo/{$tempFile[0]}.xml","wb")) {
    if(fwrite($file,$output,strlen($output))) {
        $success="YES";
        $message="File successfully built.";
    } else {
        $message="Could not write XML file.";
    }
} else {
    $message="Could not open file.";
}

Answer 1

I would venture to guess that it might have something to do with the umask, or the current permissions of the directory that you are creating the file in. Try adding sticky groups to the directory and keeping the group www-data or apache (depending on your install)

Answer 2

It does this by default because PHP assumes that you are going to read the file again. Or, in this case write to it. You might be able to change the default settings in the php.ini file.