php man page for stream_filter_prepend

STREAM_FILTER_PREPEND(3)						 1						  STREAM_FILTER_PREPEND(3)

stream_filter_prepend - Attach a filter to a stream

SYNOPSIS
       resource stream_filter_prepend (resource  $stream, string  $filtername, [int  $read_write], [mixed  $params])

DESCRIPTION
	Adds $filtername to the list of filters attached to $stream.

PARAMETERS
	      o $stream
		- The target stream.

	      o $filtername
		- The filter name.

	      o $read_write
		-  By  default,  stream_filter_prepend(3) 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(3) for an example of using this parameter.

	      o $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(3).

RETURN VALUES
	Returns a resource which can be used to refer to this filter instance during a call to stream_filter_remove(3).

CHANGELOG
       +--------+---------------------------------------------------+
       |Version |						    |
       |	|						    |
       |	|		     Description		    |
       |	|						    |
       +--------+---------------------------------------------------+
       | 5.1.0	|						    |
       |	|						    |
       |	|  Prior  to  PHP 5.1.0, this function returns TRUE |
       |	| on success or FALSE on failure.		    |
       |	|						    |
       +--------+---------------------------------------------------+
NOTES
       Note

	      When using custom (user) filters

	      stream_filter_register(3) 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(3).

       Note

	       When a filter is added for read and write, two instances of the filter are created. stream_filter_prepend(3) must be  called  twice
	      with STREAM_FILTER_READ and STREAM_FILTER_WRITE to get both filter resources.

SEE ALSO 
stream_filter_register(3), stream_filter_append(3).
PHP Documentation Group 												  STREAM_FILTER_PREPEND(3)