PHP Basics (Section 4) - Files

1. Files provide a simple temporary to permanent data store.
2. PHP5 presents two functions which make handling files, namely file_get_contents() and file_put_contents().
3. For large amounts of data, or in issues where a race condition is possible a database would be a better data store.
4. Steams are the way that PHP handles working with network resources.
5. Whenever you open up a file PHP creates a stream in the background.
6. Each stream consists of several components: file wrapper, one or two pipe-lines, an optional context, metadata about the stream.
7. Files can be locked to prevent race conditions:
   flock($fp, LOCK_SH); //Place Shared lock
   flock($fp, LOCK_EX); //
   Place Exclusive (write) Lock
   flock($fp, LOCK_UN); //Release lock
8. Placing and removing locks can inhibit performance as traffic increases, consider using a different data store.
9. Using stream context and a few other techniques a lot can be done without resorting to sockets, however for more detailed control sockets can be used.
   
10. Sockets allow read/write access to various socket connections, while things like HTTP may seem read only, at the protocol level information is being sent to identify the desired resource. Example:
    $fp = fsockopen
    ("example.preinheimer.com", 80, $errno, $errstr, 30)
    ;
    if (!$fp) {
    echo "$errstr ($errno)\n";
    } else {
    $out = "GET / HTTP/1.1\r\n";
    $out .= "Host: example.preinheimer.com\r\n";
    $out .= "Connection: Close\r\n\r\n";
    fwrite($fp, $out);
    while (!feof($fp)) {
    echo fgets($fp, 128);
    }
    fclose($fp);
    }

For more information, please read my another post Amazon S3 Makes My Document Management System Easier