Drupal 7 Module Development

Working with Files and Images
The third argument is a bitmask of options defined by PHP. The one we're
dealing with here is STREAM_REPORT_ERRORS, which indicates whether or not
PHP errors should be suppressed (for instance if a file is not found). The second is
STREAM_USE_PATH, which indicates whether PHP's include path should be checked
if a file is not found. This is not relevant to us, so we ignore it. If a file is found on
the include path, then the fourth argument $opened_url should be set with the
file's real path.
Looking at the rest of the code for stream_open(), we can see how this
comes together:
$this->uri = $uri;
$url = $this->getExternalUrl();
We save our URI into a protected property, and then call getExternalURL() to
translate it into an actual Twitpic URL that we can grab a photo from. We can then
fopen() this URL and set our internal handle.
if ($options && STREAM_REPORT_ERRORS) {
$this->handle = fopen($url, $mode);
}
else {
$this->handle = @fopen($url, $mode);
}
If STREAM_REPORT_ERRORS is not set, we suppress fopen() errors by prepending @,
which indicates to PHP that errors should not be reported. It is always good coding
practice to properly handle the options available to your stream functions if they are
applicable to your user case.
In addition to creating an implementation of DrupalStreamWrapperInterface,
modules that define their own stream wrappers must register them with Drupal's
stream wrapper registry by implementing hook_stream_wrappers(). This hook
returns an associative array defining some information about our stream wrapper,
as shown in the following code:
/**
* Implement hook_stream_wrappers().
*/
function twitpic_stream_wrappers() {{
return array(
'twitpic' => array(
'name' => 'Twitpic photos',
'class' => 'TwitpicStreamWrapper',
'description' => t('Photos from the Twitpic hosting service.')
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