ob_start
(PHP 4, PHP 5)
ob_start — Turn on output buffering
Описание
bool ob_start
([
callback $output_callback
[,
int $chunk_size
[,
bool $erase
]]] )
The contents of this internal buffer may be copied into a string variable
using ob_get_contents(). To output what is stored in
the internal buffer, use ob_end_flush(). Alternatively,
ob_end_clean() will silently discard the buffer
contents.
Внимание
Some web servers (e.g. Apache) change the working directory of a script
when calling the callback function. You can change it back by e.g.
chdir(dirname($_SERVER['SCRIPT_FILENAME'])) in the
callback function.
Output buffers are stackable, that is, you may call
ob_start() while another
ob_start() is active. Just make
sure that you call ob_end_flush()
the appropriate number of times. If multiple output callback
functions are active, output is being filtered sequentially
through each of them in nesting order.
Список параметров
-
output_callback
-
An optional output_callback
function may be
specified. This function takes a string as a parameter and should
return a string. The function will be called when
the output buffer is flushed (sent) or cleaned (with
ob_flush(), ob_clean() or similar
function) or when the output buffer
is flushed to the browser at the end of the request. When
output_callback
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 output_callback
is not a
callable function, this function will return FALSE.
If the callback function has two parameters, the second parameter is
filled with a bit-field consisting of
PHP_OUTPUT_HANDLER_START,
PHP_OUTPUT_HANDLER_CONT and
PHP_OUTPUT_HANDLER_END.
If output_callback
returns FALSE original
input is sent to the browser.
The output_callback
parameter may be bypassed
by passing a NULL value.
ob_end_clean(), ob_end_flush(),
ob_clean(), ob_flush() and
ob_start() 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
print_r($expression, true) or
highlight_file($filename, true) from a callback
function.
Замечание:
In PHP 4.0.4, ob_gzhandler() was introduced to
facilitate sending gz-encoded data to web browsers that support
compressed web pages. ob_gzhandler() determines
what type of content encoding the browser will accept and will return
its output accordingly.
-
chunk_size
-
If the optional parameter chunk_size
is passed, the
buffer will be flushed after any output call which causes the buffer's
length to equal or exceed chunk_size
.
Default value 0 means that the function is called only in the end,
other special value 1 sets chunk_size
to 4096.
-
erase
-
If the optional parameter erase
is set to FALSE,
the buffer will not be deleted until the script finishes (as of PHP 4.3.0).
Возвращаемые значения
Возвращает TRUE в случае успешного завершения или FALSE в случае возникновения ошибки.
Примеры
Пример #1 User defined callback function example
<?php
function callback($buffer)
{
// replace all the apples with oranges
return (str_replace("apples", "oranges", $buffer));
}
ob_start("callback");
?>
<html>
<body>
<p>It's like comparing apples to oranges.</p>
</body>
</html>
<?php
ob_end_flush();
?>
Результат выполнения данного примера:
<html>
<body>
<p>It's like comparing oranges to oranges.</p>
</body>
</html>
