stream_filter_prepend
(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
Attach a filter to a stream
Description
Adds filter_name to the list of filters attached to stream.
Parameters
streamThe target stream.
filter_nameThe filter name.
modeBy default,
stream_filter_prepend()will attach the filter to theread filter chainif the file was opened for reading (i.e. File Mode:r, and/or+). The filter will also be attached to thewrite filter chainif the file was opened for writing (i.e. File Mode:w,a, and/or+).STREAM_FILTER_READ,STREAM_FILTER_WRITE, and/orSTREAM_FILTER_ALLcan also be passed to themodeparameter to override this behavior. Seestream_filter_append()for an example of using this parameter.paramsThis filter will be added with the specified
paramsto the beginning of the list and will therefore be called first during stream operations. To add a filter to the end of the list, usestream_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 filter_name cannot be located.
Notes
stream_filter_register() must be called first in order to register the desired user filter to filter_name.
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().
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.