Is there a guaranteed file resource on PHP?

Question

Is there some url/stream that fopen will successfully open on most PHP installations? /dev/null is not available or openable on some systems. Something like php://temp should be a fairly safe bet, right?

The application for this code that guarantees a file resource, instead of the mixed filetype of bool|resource you have with fopen:

/**
 * @return resource
 */
function openFileWithResourceGuarantee() {
    $fh = @fopen('/write/protected/location.txt', 'w');
    if ( $fh === false ) {
        error_log('Could not open /write/protected/location.txt');
        $fh = fopen('php://temp');
    }
    return $fh;
}

In PHP 7 with strict types, the above function should guarantee a resource and avoid bools. I know that resources are not official types, but still want to be as type-safe as possible.

Answer 1

php://memory should be universally available.