stream_filter_prepend
Attach a filter to a stream
Description
resource stream_filter_prepend(
resource $stream,
string $filtername,
int $read_write = ?,
mixed $params = ?
)
Parameters
-
stream
-
The target stream.
-
filtername
-
The filter name.
-
read_write
-
By default, stream_filter_prepend will
attach the filter to the read filter chain
if the file was opened for reading (i.e. File Mode:
r, and/or +). The filter
will also be attached to the write filter chain
if the file was opened for writing (i.e. File Mode:
w, a, and/or +).
STREAM_FILTER_READ,
STREAM_FILTER_WRITE, and/or
STREAM_FILTER_ALL can also be passed to the
read_write parameter to override this behavior.
See stream_filter_append for an example of
using this parameter.
-
params
-
This filter will be added with the specified params
to the beginning of the list and will therefore be
called first during stream operations. To add a filter to the end of the
list, use stream_filter_append.
Return Values
Returns a resource on success or false on failure. The resource can be
used to refer to this filter instance during a call to
stream_filter_remove.
false is returned if stream is not a resource or
if filtername cannot be located.
Notes
Note:
When using custom (user) filters
stream_filter_register must be called first
in order to register the desired user filter to filtername.
Note:
Stream data is read from resources (both local and remote) in chunks,
with any unconsumed data kept in internal buffers. When a new
filter is prepended to a stream, data in the internal buffers,
which has already been processed through other filters will
not be reprocessed through the new filter
at that time. This differs from the behavior of
stream_filter_append.
Note:
When a filter is added for read and write, two instances of the filter
are created. stream_filter_prepend must be called twice
with STREAM_FILTER_READ and
STREAM_FILTER_WRITE to get both filter resources.
See Also
- stream_filter_register
- stream_filter_append