Having problems reading/writing the php://temp stream

php://temp is not a file path, it's a pseudo protocol that always creates a new random temp file when used. The /test is actually being ignored entirely. The only extra "arguments" the php://temp wrapper accepts is /maxmemory:n. You need to keep a file handle around to the opened temp stream, or it will be discarded:

$tmp = fopen('php://temp', 'r+');
fwrite($tmp, 'test');
rewind($tmp);
fpassthru($tmp);
fclose($tmp);

See http://php.net/manual/en/wrappers.php.php#refsect1-wrappers.php-examples

Each time, when you use fopen to get handler, content of php://temp will be flushed. Use rewind() and stream_get_contents() to get content. Or, use normal cachers, like APC or memcache :)