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>stream_filter_prepend</H1
><DIV
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><A
NAME="AEN222960"
></A
><P
> (PHP 4 >= 4.3.0, PHP 5)</P
>stream_filter_prepend -- Attach a filter to a stream</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN222963"
></A
><H2
>Description</H2
>resource <B
CLASS="methodname"
>stream_filter_prepend</B
> ( resource stream, string filtername [, int read_write [, mixed params]] )<BR
></BR
><P
> Adds <CODE
CLASS="parameter"
>filtername</CODE
> to the list of filters
attached to <CODE
CLASS="parameter"
>stream</CODE
>. This filter will be
added with the specified <CODE
CLASS="parameter"
>params</CODE
>
to the <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>beginning</I
></SPAN
> of the list and
will therefore be called first during stream operations. To
add a filter to the end of the list, use
<A
HREF="function.stream-filter-append.html"
><B
CLASS="function"
>stream_filter_append()</B
></A
>.
</P
><P
> By default, <B
CLASS="function"
>stream_filter_prepend()</B
> will
attach the filter to the <TT
CLASS="literal"
>read filter chain</TT
>
if the file was opened for reading (i.e. File Mode:
<TT
CLASS="literal"
>r</TT
>, and/or <TT
CLASS="literal"
>+</TT
>). The filter
will also be attached to the <TT
CLASS="literal"
>write filter chain</TT
>
if the file was opened for writing (i.e. File Mode:
<TT
CLASS="literal"
>w</TT
>, <TT
CLASS="literal"
>a</TT
>, and/or <TT
CLASS="literal"
>+</TT
>).
<TT
CLASS="constant"
><B
>STREAM_FILTER_READ</B
></TT
>,
<TT
CLASS="constant"
><B
>STREAM_FILTER_WRITE</B
></TT
>, and/or
<TT
CLASS="constant"
><B
>STREAM_FILTER_ALL</B
></TT
> can also be passed to the
<CODE
CLASS="parameter"
>read_write</CODE
> parameter to override this behavior.
See <A
HREF="function.stream-filter-append.html"
><B
CLASS="function"
>stream_filter_append()</B
></A
> for an example of
using this parameter.
</P
><P
> As of PHP 5.1.0, this function returns a resource which
can be used to refer to this filter instance during a call
to <A
HREF="function.stream-filter-remove.html"
><B
CLASS="function"
>stream_filter_remove()</B
></A
>.
Prior to PHP 5.1.0, this function returns <TT
CLASS="constant"
><B
>TRUE</B
></TT
> on success
or <TT
CLASS="constant"
><B
>FALSE</B
></TT
> on failure.
</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>When using custom (user) filters: </B
>
<A
HREF="function.stream-filter-register.html"
><B
CLASS="function"
>stream_filter_register()</B
></A
> must be called first
in order to register the desired user filter to <CODE
CLASS="parameter"
>filtername</CODE
>.
</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
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
<SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>not</I
></SPAN
> be reprocessed through the new filter
at that time. This differs from the behavior of
<A
HREF="function.stream-filter-append.html"
><B
CLASS="function"
>stream_filter_append()</B
></A
>.
</P
></BLOCKQUOTE
></DIV
><P
> See also
<A
HREF="function.stream-filter-register.html"
><B
CLASS="function"
>stream_filter_register()</B
></A
>, and
<A
HREF="function.stream-filter-append.html"
><B
CLASS="function"
>stream_filter_append()</B
></A
>.
</P
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