(PHP 4, PHP 5)
ob_start — Turn on output buffering
([ callback $output_callback
[, int $chunk_size
[, bool $erase
The contents of this internal buffer may be copied into a string variable
using ob_get_contents(). To output what is stored in
the internal buffer, use ob_end_flush(). Alternatively,
ob_end_clean() will silently discard the buffer
Some web servers (e.g. Apache) change the working directory of a script
when calling the callback function. You can change it back by e.g.
chdir(dirname($_SERVER['SCRIPT_FILENAME'])) in the
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.
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
ob_end_flush() is called, or when the output buffer
is flushed to the browser at the end of the request. When
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
returns FALSE original
input is sent to the browser.
parameter may be bypassed
by passing a NULL value.
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
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.
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
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).
Returns TRUE on success or FALSE on failure.
This function was changed to return FALSE in case the passed
can not be executed.
Example #1 User defined callback function example
// replace all the apples with oranges
return (str_replace("apples", "oranges", $buffer));
<p>It's like comparing apples to oranges.</p>
The above example will output:
<p>It's like comparing oranges to oranges.</p>