stream_filter_prepend
(PHP 4 >= 4.3.0, PHP 5, PHP 7)
stream_filter_prepend — Attach a filter to a stream
说明
$stream ,
string $filtername [,
int $read_write [,
mixed $params ]] ) :
resource
Adds filtername to the list of filters attached to stream.
参数
-
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/orSTREAM_FILTER_ALLcan also be passed to theread_writeparameter to override this behavior. See stream_filter_append() for an example of using this parameter. -
params -
This 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, use stream_filter_append().
返回值
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.
更新日志
| 版本 | 说明 |
|---|---|
| 5.1.0 | Prior to PHP 5.1.0, this function returns TRUE on success 或者在失败时返回 FALSE. |
注释
Note: When using custom (user) filters
stream_filter_register() must be called first in order to register the desired user filter tofiltername.
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_READandSTREAM_FILTER_WRITEto get both filter resources.
参见
- stream_filter_register() - Register a user defined stream filter
- stream_filter_append() - Attach a filter to a stream
