ob_start
(PHP 4 )
ob_start -- Turn on output buffering
Description
bool ob_start ( [callback output_callback])
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.
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.
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 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.
Note: 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.
Note: Before PHP 4.3.2 this function did not return FALSE
in case the passed output_callback can not be executed.
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.
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.
Example 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.
</body>
</html>
<?php
ob_end_flush();
?>
Would produce:
<html>
<body>
<p>It's like comparing oranges to oranges.
</body>
</html>
See also ob_get_contents(), ob_end_flush(), ob_end_clean(),
ob_implicit_flush() and ob_gzhandler().
