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php-manual-zh-5.2.4-1mdv2008.1.noarch.rpm

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><H1
><A
NAME="function.ob-start"
></A
>ob_start</H1
><DIV
CLASS="refnamediv"
><A
NAME="AEN165880"
></A
><P
>    (PHP 4, PHP 5)</P
>ob_start&nbsp;--&nbsp;Turn on output buffering</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN165883"
></A
><H2
>Description</H2
>bool <B
CLASS="methodname"
>ob_start</B
> ( [callback output_callback [, int chunk_size [, bool erase]]] )<BR
></BR
><P
>&#13;     This function will turn output buffering on. While output
     buffering is active no output is sent from the script (other than
     headers), instead the output is stored in an internal buffer.
    </P
><P
>&#13;     The contents of this internal buffer may be copied into a string
     variable using <A
HREF="function.ob-get-contents.html"
><B
CLASS="function"
>ob_get_contents()</B
></A
>.  To output
     what is stored in the internal buffer, use
     <A
HREF="function.ob-end-flush.html"
><B
CLASS="function"
>ob_end_flush()</B
></A
>.  Alternatively,
     <A
HREF="function.ob-end-clean.html"
><B
CLASS="function"
>ob_end_clean()</B
></A
> will silently discard the
     buffer contents.
    </P
><P
>&#13;     An optional <CODE
CLASS="parameter"
>output_callback</CODE
> function may
     be specified. This function takes a string as a parameter and
     should return a string. The function will be called when
     <A
HREF="function.ob-end-flush.html"
><B
CLASS="function"
>ob_end_flush()</B
></A
> is called, or when the output
     buffer is flushed to the browser at the end of the request.  When
     <CODE
CLASS="parameter"
>output_callback</CODE
> is called, it will receive
     the contents of the output buffer as its parameter and is
     expected to return a new output buffer as a result, which will be
     sent to the browser. If the <CODE
CLASS="parameter"
>output_callback</CODE
> is not
     a callable function, this function will return <TT
CLASS="constant"
><B
>FALSE</B
></TT
>.
     If the callback function has two parameters, the second parameter is filled
     with a bit-field consisting of
     <TT
CLASS="constant"
><B
>PHP_OUTPUT_HANDLER_START</B
></TT
>,
     <TT
CLASS="constant"
><B
>PHP_OUTPUT_HANDLER_CONT</B
></TT
> and
     <TT
CLASS="constant"
><B
>PHP_OUTPUT_HANDLER_END</B
></TT
>.
     If <CODE
CLASS="parameter"
>output_callback</CODE
> returns <TT
CLASS="constant"
><B
>FALSE</B
></TT
> original input
     is sent to the browser.
    </P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
      In PHP 4.0.4, <A
HREF="function.ob-gzhandler.html"
><B
CLASS="function"
>ob_gzhandler()</B
></A
> was introduced
      to facilitate sending gz-encoded data to web browsers that
      support compressed web pages.  <A
HREF="function.ob-gzhandler.html"
><B
CLASS="function"
>ob_gzhandler()</B
></A
>
      determines what type of content encoding the browser will accept
      and will return its output accordingly.
     </P
></BLOCKQUOTE
></DIV
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
      Before PHP 4.3.2 this function did not return <TT
CLASS="constant"
><B
>FALSE</B
></TT
> in case the passed
      <CODE
CLASS="parameter"
>output_callback</CODE
> can not be executed.
     </P
></BLOCKQUOTE
></DIV
><DIV
CLASS="warning"
><P
></P
><TABLE
CLASS="warning"
BORDER="1"
WIDTH="100%"
><TR
><TD
ALIGN="CENTER"
><B
>警告</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
>&#13;      Some web servers (e.g. Apache) change the working directory of a script
      when calling the callback function. You can change it back by e.g.
      <TT
CLASS="literal"
>chdir(dirname($_SERVER['SCRIPT_FILENAME']))</TT
> in the
      callback function.
     </P
></TD
></TR
></TABLE
></DIV
><P
>&#13;     If the optional parameter <CODE
CLASS="parameter"
>chunk_size</CODE
> is passed, the
     callback function is called on every first newline after
     <CODE
CLASS="parameter"
>chunk_size</CODE
> bytes of output.
     The <CODE
CLASS="parameter"
>output_callback</CODE
> parameter may be bypassed by
     passing a <TT
CLASS="constant"
><B
>NULL</B
></TT
> value.
    </P
><P
>&#13;     If the optional parameter <CODE
CLASS="parameter"
>erase</CODE
> is set to <TT
CLASS="constant"
><B
>FALSE</B
></TT
>,
     the buffer will not be deleted until the script finishes (as of PHP 4.3.0).
    </P
><P
>&#13;     Output buffers are stackable, that is, you may call
     <B
CLASS="function"
>ob_start()</B
> while another
     <B
CLASS="function"
>ob_start()</B
> is active. Just make
     sure that you call <A
HREF="function.ob-end-flush.html"
><B
CLASS="function"
>ob_end_flush()</B
></A
>
     the appropriate number of times. If multiple output callback
     functions are active, output is being filtered sequentially
     through each of them in nesting order.
    </P
><P
>&#13;     <A
HREF="function.ob-end-clean.html"
><B
CLASS="function"
>ob_end_clean()</B
></A
>,
     <A
HREF="function.ob-end-flush.html"
><B
CLASS="function"
>ob_end_flush()</B
></A
>, <A
HREF="function.ob-clean.html"
><B
CLASS="function"
>ob_clean()</B
></A
>,
     <A
HREF="function.ob-flush.html"
><B
CLASS="function"
>ob_flush()</B
></A
> and <B
CLASS="function"
>ob_start()</B
>
     may not be called from a callback function. If you call them from
     callback function, the behavior is undefined. If you would like to
     delete the contents of a buffer, return "" (a null string) from callback
     function.
     You can't even call functions using the output buffering functions like
     <TT
CLASS="literal"
>print_r($expression, true)</TT
> or
     <TT
CLASS="literal"
>highlight_file($filename, true)</TT
> from a callback
     function.
    </P
><P
>&#13;     <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN165945"
></A
><P
><B
>例 1. User defined callback function example</B
></P
><TABLE
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><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br /><br /></font><font color="#007700">function </font><font color="#0000BB">callback</font><font color="#007700">(</font><font color="#0000BB">$buffer</font><font color="#007700">) <br />{<br />&nbsp;&nbsp;</font><font color="#FF8000">// replace all the apples with oranges<br />&nbsp;&nbsp;</font><font color="#007700">return (</font><font color="#0000BB">str_replace</font><font color="#007700">(</font><font color="#DD0000">"apples"</font><font color="#007700">, </font><font color="#DD0000">"oranges"</font><font color="#007700">, </font><font color="#0000BB">$buffer</font><font color="#007700">));<br />}<br /><br /></font><font color="#0000BB">ob_start</font><font color="#007700">(</font><font color="#DD0000">"callback"</font><font color="#007700">);<br /><br /></font><font color="#0000BB">?&gt;<br /></font>&lt;html&gt;<br />&lt;body&gt;<br />&lt;p&gt;It's like comparing apples to oranges.&lt;/p&gt;<br />&lt;/body&gt;<br />&lt;/html&gt;<br /><font color="#0000BB">&lt;?php<br /><br />ob_end_flush</font><font color="#007700">();<br /><br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
><P
>&#13;       Would produce:
      </P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>&#60;html&#62;
&#60;body&#62;
&#60;p&#62;It's like comparing oranges to oranges.&#60;/p&#62;
&#60;/body&#62;
&#60;/html&#62;</PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
    </P
><P
>&#13;     See also <A
HREF="function.ob-get-contents.html"
><B
CLASS="function"
>ob_get_contents()</B
></A
>,
     <A
HREF="function.ob-end-flush.html"
><B
CLASS="function"
>ob_end_flush()</B
></A
>,
     <A
HREF="function.ob-end-clean.html"
><B
CLASS="function"
>ob_end_clean()</B
></A
>,
     <A
HREF="function.ob-implicit-flush.html"
><B
CLASS="function"
>ob_implicit_flush()</B
></A
>,
     <A
HREF="function.ob-gzhandler.html"
><B
CLASS="function"
>ob_gzhandler()</B
></A
>, <A
HREF="function.ob-iconv-handler.html"
><B
CLASS="function"
>ob_iconv_handler()</B
></A
>
     <A
HREF="function.mb-output-handler.html"
><B
CLASS="function"
>mb_output_handler()</B
></A
>, and
     <A
HREF="function.ob-tidyhandler.html"
><B
CLASS="function"
>ob_tidyhandler()</B
></A
>.
    </P
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