This is a native mmap extension for PHP. It's been put together from a few bits and pieces and is designed to be a drop-in replacement for php-mmap to improve performance.
Installing custom php extensions is a pain, but if you have all the tools (php5-dev, gcc etc) installed, it's pretty easy
$ phpize
$ ./configure
$ sudo make install
Then it's just a matter of enabling the extension in your php.ini by adding the following line:
extension=mmap.so
Calling the mmap_open() function will return a stream resource that can be used with fread(), fwrite(), fseek(), fclose()
//mmap_open($file_name, $block_size, $offset)
$mmap = mmap_open('/dev/mem', 1024, 0);