(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
stream_filter_prepend — Attach a filter to a stream
$stream
, string $filtername
, int $read_write = ?
, mixed $params = ?
) : resource
Adds filtername to the list of filters
attached to stream.
streamThe target stream.
filternameThe 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().
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.
注意: When using custom (user) filters
stream_filter_register() must be called first in order to register the desired user filter tofiltername.
注意: 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().
注意: 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_READandSTREAM_FILTER_WRITEto get both filter resources.